From b20ac0164dd830eda64426b076322d7ac9365d20 Mon Sep 17 00:00:00 2001
From: Scott Little <scott.little@windriver.com>
Date: Wed, 5 Sep 2018 16:56:37 -0400
Subject: [PATCH] Build Avoidance

Purpose:
   Reduce build times after a repo sync by pulling in pre-generated
srpms and rpms and other build products created by a local reference build.

Usage:
  repo sync
  generate-cgcs-centos-repo.sh ...
  populate_downloads.sh ...
  build-pkgs --build-avoidance [--build-avoidance-user <user> \
     --build-avoidance-host <addr> --build-avoidance-dir <dir>]

Reference builds:
- A server performs a regular (daily?), automated builds using
  existing methods. Call these the reference builds.

- The builds are timestamped, and preserved for some time. (weeks?)
  The MY_WORKSPACE directory for the build shall have a common root
  directory, and a leaf directory that is a UTC time stamp of format
  YYYYMMDDThhmmssZ.
  e.g.
  MY_WORKSPACE=/localdisk/loadbuild/jenkins/StarlingX/20180719T113021Z

  Alternative formats are possible by setting values in ...
  "$MY_REPO/local-build-data/build_avoidance_source"
  e.g.
  BUILD_AVOIDANCE_DATE_FORMAT="%Y-%m-%d"
  BUILD_AVOIDANCE_TIME_FORMAT="%H-%M-%S"
  BUILD_AVOIDANCE_DATE_TIME_DELIM="_"
  BUILD_AVOIDANCE_DATE_TIME_POSTFIX=""
  BUILD_AVOIDANCE_DATE_UTC=0

  Which results in YYYY-MM-DD_hh-mm-ss format using local time.
  The one property that the timestamp must have is that they
  are sortable, and that the reference build and the consumer of
  the reference builds agree on the format.

- A build CONTEXT is captured, consisting of the SHA of each and every
  git that contributed to the build.

- For each package built, a file shall capture he md5sums of all the
  source code inputs to the build of that package.

- All these build products are accessible locally (e.g. a regional
  office) via rsync (other protocols can be added later).  ssh
  is also required to run remote query commands on the reference build.

  Initial ground work to support a selection variable ....
  BUILD_AVOIDANCE_FILE_TRANSFER="my-transfer-protocol"
  in $MY_REPO/local-build-data/build_avoidance_source"
  has been created, but "rsync" is the only valid value at this time.

- Location of the reference build can be specified via command line, or
  defaults can be put in $MY_REPO/local-build-data/build_avoidance_source.
  The local-build-data directory is gitignored by stx-root and so can be
  customized for local needs.
  e.g.
  cat $MY_REPO/local-build-data/build_avoidance_source
  BUILD_AVOIDANCE_USR="jenkins"
  BUILD_AVOIDANCE_HOST="stx-build-server.myco.com"
  BUILD_AVOIDANCE_DIR="/localdisk/loadbuild/jenkins/StarlingX"

Notes:
- Build avoidance is only used if requested.
- Build avoidance does not necessarily use the latest reference build.
  It compares the git context of all available reference builds vs your
  own git context, and chooses the most recent for which you gits have
  all the conent.  i.e. all your gits will be same or newer than that
  used by the reference build.  This also meens that some packages might
  still need to be rebuilt after the download step.
- Normally build avoidance remembers the last download context and will only
  consider reference builds newer than the last download.   You can reset
  using 'build-pkgs --build-avoidance --clear' to erase the download history.
  When might this matter to me?  If you change to an old branch that
  hasn't been synced recently and want to build in that context.
- The primary assumtion of Build Avoidance is that it is faster to
  download packages than to build them.  This is typically true of a
  good LAN, but likely not true of a WAN. This is why we emphasize the
  local nature of your reference build server.

Also in this update:
- reworked context generation to be relative to 'dirname $MY_REPO'
- Moved md5sum calculation to a common file, and fixed case where
  symlinks where canonacalized to paths outside of $MY_REPO.
  We'll make an exception to canonacalization to keep paths
  relative to $MY_REPO.
- In future other functions could be moved to the common file.

Story: 2002835
Task: 22754
Change-Id: I757780190cc6063d0a2d3ad9d0a6020ab5169e99
Signed-off-by: Scott Little <scott.little@windriver.com>
---
 .gitignore                           |   1 +
 build-data/build_avoidance_source    |  23 +
 build-tools/build-avoidance-utils.sh | 842 +++++++++++++++++++++++++++
 build-tools/build-pkgs               |   3 +
 build-tools/build-pkgs-parallel      | 124 +++-
 build-tools/build-pkgs-serial        | 163 +++++-
 build-tools/build-rpms               |  10 +
 build-tools/build-rpms-parallel      |  28 +-
 build-tools/build-rpms-serial        |  26 +-
 build-tools/build-srpms              |  18 +
 build-tools/build-srpms-common.sh    | 187 ++++++
 build-tools/build-srpms-parallel     |  77 ++-
 build-tools/build-srpms-serial       |  75 +--
 build-tools/git-utils.sh             |  57 +-
 build-tools/sign-secure-boot         |   8 +-
 15 files changed, 1491 insertions(+), 151 deletions(-)
 create mode 100644 build-data/build_avoidance_source
 create mode 100644 build-tools/build-avoidance-utils.sh
 create mode 100644 build-tools/build-srpms-common.sh

diff --git a/.gitignore b/.gitignore
index 7770dd90..df27462f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 /cgcs-centos-repo
 /cgcs-tis-repo
 /cgcs-3rd-party-repo
+/local-build-data
diff --git a/build-data/build_avoidance_source b/build-data/build_avoidance_source
new file mode 100644
index 00000000..71135f20
--- /dev/null
+++ b/build-data/build_avoidance_source
@@ -0,0 +1,23 @@
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+
+#
+# What files and directories need to be copied
+#
+BUILD_AVOIDANCE_SRPM_DIRECTORIES="inputs srpm_assemble rpmbuild/SRPMS rpmbuild/SOURCES"
+BUILD_AVOIDANCE_SRPM_FILES=""
+BUILD_AVOIDANCE_RPM_DIRECTORIES="results rpmbuild/RPMS rpmbuild/SPECS"
+BUILD_AVOIDANCE_RPM_FILES=".platform_release"
+
+
+#
+# Copy the lines below to $MY_REPO/local-build-data/build_avoidance_source,
+# then uncomment and fill in the values giving the location of your local reference build.
+#
+# BUILD_AVOIDANCE_USR="jenkins"
+# BUILD_AVOIDANCE_HOST="machine.corp.com"
+# BUILD_AVOIDANCE_DIR="/localdisk/loadbuild/jenkins/StarlingX_Build"
diff --git a/build-tools/build-avoidance-utils.sh b/build-tools/build-avoidance-utils.sh
new file mode 100644
index 00000000..d728c760
--- /dev/null
+++ b/build-tools/build-avoidance-utils.sh
@@ -0,0 +1,842 @@
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+#
+# Functions related to build avoidance.
+#
+# Do not call directly.  Used by build-pkgs.
+#
+# Build avoidance downloads rpm, src.rpm and other artifacts of
+# build-pkgs for a local reference build.  The reference would
+# typically be an automated build run atleast daily.
+# The MY_WORKSPACE directory for the reference build shall have
+# a common root directory, and a leaf directory that is a time stamp
+# in a sortable parsable format.   Default YYYYMMDDThhmmssZ.
+#  e.g. /localdisk/loadbuild/jenkins/StarlingX/20180719T113021Z
+#
+# Other formats can be used by setting the following variables
+# in $MY_REPO/local-build-data/build_avoidance_source.
+#   e.g. to allow format YYYY-MM-DD_hh-mm-ss
+# BUILD_AVOIDANCE_DATE_FORMAT="%Y-%m-%d"
+# BUILD_AVOIDANCE_TIME_FORMAT="%H-%M-%S"
+# BUILD_AVOIDANCE_DATE_TIME_DELIM="_"
+# BUILD_AVOIDANCE_DATE_TIME_POSTFIX=""
+#
+# Note: Must be able to rsync and ssh to the machine that holds the
+# reference builds.
+#
+# In future alternative transfer protocols may be supported.
+# Select the alternate protocol by setting the following variables
+# in $MY_REPO/local-build-data/build_avoidance_source.
+# e.g.
+# BUILD_AVOIDANCE_FILE_TRANSFER="my-supported-prototcol"
+#
+
+BUILD_AVOIDANCE_USR=""
+BUILD_AVOIDANCE_HOST=""
+BUILD_AVOIDANCE_DIR=""
+BUILD_AVOIDANCE_URL=""
+
+# Default date/time format, iso-8601 compact, 20180912T143913Z
+# Syntax is a subset of that use by the unix 'date' command.
+BUILD_AVOIDANCE_DATE_FORMAT="%Y%m%d"
+BUILD_AVOIDANCE_TIME_FORMAT="%H%M%S"
+BUILD_AVOIDANCE_DATE_TIME_DELIM="T"
+BUILD_AVOIDANCE_DATE_TIME_POSTFIX="Z"
+
+# Default file transfer method
+BUILD_AVOIDANCE_FILE_TRANSFER="rsync"
+
+# Default is to use timestamps and days in UTC
+#
+# If you prefer local time, then set 'BUILD_AVOIDANCE_DATE_UTC=0'
+# in '$MY_REPO/local-build-data/build_avoidance_source'
+BUILD_AVOIDANCE_DATE_UTC=1
+
+BUILD_AVOIDANCE_DATA_DIR="$MY_WORKSPACE/build_avoidance_data"
+BUILD_AVOIDANCE_SOURCE="$MY_REPO/build-data/build_avoidance_source"
+BUILD_AVOIDANCE_LOCAL_SOURCE="$MY_REPO/local-build-data/build_avoidance_source"
+BUILD_AVOIDANCE_TEST_CONTEXT="$BUILD_AVOIDANCE_DATA_DIR/test_context"
+BUILD_AVOIDANCE_LAST_SYNC_FILE="$BUILD_AVOIDANCE_DATA_DIR/last_sync_context"
+
+if [ ! -f $BUILD_AVOIDANCE_SOURCE ]; then
+    echo "Couldn't read $BUILD_AVOIDANCE_SOURCE"
+    exit 1
+fi
+
+echo "Reading: $BUILD_AVOIDANCE_SOURCE"
+source $BUILD_AVOIDANCE_SOURCE
+
+if [ -f $BUILD_AVOIDANCE_LOCAL_SOURCE ]; then
+    echo "Reading: $BUILD_AVOIDANCE_LOCAL_SOURCE"
+    source $BUILD_AVOIDANCE_LOCAL_SOURCE
+fi
+
+UTC=""
+
+if [ $BUILD_AVOIDANCE_DATE_UTC -eq 1 ]; then
+    UTC="--utc"
+fi
+
+
+if [ "x$BUILD_AVOIDANCE_OVERRIDE_DIR" != "x" ]; then
+    BUILD_AVOIDANCE_DIR="$BUILD_AVOIDANCE_OVERRIDE_DIR"
+fi
+
+if [ "x$BUILD_AVOIDANCE_OVERRIDE_HOST" != "x" ]; then
+    BUILD_AVOIDANCE_HOST="$BUILD_AVOIDANCE_OVERRIDE_HOST"
+fi
+
+if [ "x$BUILD_AVOIDANCE_OVERRIDE_USR" != "x" ]; then
+    BUILD_AVOIDANCE_USR="$BUILD_AVOIDANCE_OVERRIDE_USR"
+fi
+
+echo "BUILD_AVOIDANCE_DIR=$BUILD_AVOIDANCE_DIR"
+echo "BUILD_AVOIDANCE_HOST=$BUILD_AVOIDANCE_HOST"
+echo "BUILD_AVOIDANCE_USR=$BUILD_AVOIDANCE_USR"
+
+build_avoidance_clean () {
+    if [ -f $BUILD_AVOIDANCE_LAST_SYNC_FILE ]; then
+        \rm -f -v "$BUILD_AVOIDANCE_LAST_SYNC_FILE"
+    fi
+}
+
+
+date_to_iso_8601 () {
+    local DATE="$1"
+    local CENTURY=""
+    local YEAR_IN_CENTURY="00"
+    local MONTH="01"
+    local DAY="01"
+    local DAY_OF_YEAR=""
+
+    CENTURY="$(date  '+%C')"
+
+    for x in $(echo "${BUILD_AVOIDANCE_DATE_FORMAT}" | tr ' ' '#' | sed 's/%%/#/g' | tr '%' ' ' ); do
+        # Consume format case options
+        case ${x:0:1} in
+            ^) x=${x:1};;
+            \#) x=${x:1};;
+            *) ;;
+        esac
+
+        # Process format
+        case $x in
+            Y*)  CENTURY=${DATE:0:2}; YEAR_IN_CENTURY=${DATE:2:2}; DATE=${DATE:4}; x=${x:1};;
+            0Y*) CENTURY=${DATE:0:2}; YEAR_IN_CENTURY=${DATE:2:2}; DATE=${DATE:4}; x=${x:2};;
+            _Y*) CENTURY=$(echo "${DATE:0:2}" | tr ' ' '0'); YEAR_IN_CENTURY=${DATE:2:2}; DATE=${DATE:4}; x=${x:2};;
+
+            y*)  YEAR_IN_CENTURY=${DATE:0:2}; DATE=${DATE:2}; x=${x:1};;
+            0y*) YEAR_IN_CENTURY=${DATE:0:2}; DATE=${DATE:2}; x=${x:2};;
+            _y*) YEAR_IN_CENTURY=$(echo "${DATE:0:2}" | tr ' ' '0'); DATE=${DATE:2}; x=${x:2};;
+
+            C*)  CENTURY=${DATE:0:2}; DATE=${DATE:2}; x=${x:1};;
+            0C*) CENTURY=${DATE:0:2}; DATE=${DATE:2}; x=${x:2};;
+            _C*) CENTURY=$(echo "${DATE:0:2}" | tr ' ' '0'); DATE=${DATE:2}; x=${x:2};;
+
+            m*)  MONTH=${DATE:0:2}; DATE=${DATE:2}; x=${x:1};;
+            0m*) MONTH=${DATE:0:2}; DATE=${DATE:2}; x=${x:2};;
+            _m*) MONTH=$(echo "${DATE:0:2}" | tr ' ' '0'); DATE=${DATE:2}; x=${x:2};;
+            e*)  MONTH=$(echo "${DATE:0:2}" | tr ' ' '0'); DATE=${DATE:2}; x=${x:1};;
+            0e*) MONTH=${DATE:0:2}; DATE=${DATE:2}; x=${x:2};;
+            _e*) MONTH=$(echo "${DATE:0:2}" | tr ' ' '0'); DATE=${DATE:2}; x=${x:2};;
+            b*)  MONTH="$(date -d "${DATE:0:3} 1 2000" '+%m')"; DATE=${DATE:3}; x=${x:1};;
+            h*)  MONTH="$(date -d "${DATE:0:3} 1 2000" '+%m')"; DATE=${DATE:3}; x=${x:1};;
+
+            d*)  DAY=${DATE:0:2}; DATE=${DATE:2}; x=${x:1};;
+            0d*) DAY=${DATE:0:2}; DATE=${DATE:2}; x=${x:2};;
+            _d*) DAY=$(echo "${DATE:0:2}" | tr ' ' '0'); DATE=${DATE:2}; x=${x:2};;
+
+            j*)  DAY_OF_YEAR=${DATE:0:3}; DATE=${DATE:3}; x=${x:1};;
+            0j*) DAY_OF_YEAR=${DATE:0:3}; DATE=${DATE:3}; x=${x:2};;
+            _j*) DAY_OF_YEAR=$(echo "${DATE:0:3}" | tr ' ' '0'); DATE=${DATE:3}; x=${x:2};;
+
+            D*) MONTH=${DATE:0:2}; DAY=${DATE:3:2}; YEAR_IN_CENTURY=${DATE:6:2}; DATE=${DATE:8}; x=${x:1};;
+            F*) CENTURY=${DATE:0:2}; YEAR_IN_CENTURY=${DATE:2:2}; MONTH=${DATE:5:2}; DAY=${DATE:8:2}; DATE=${DATE:10}; x=${x:1};;
+            *) >&2 echo "$FUNCNAME (${LINENO}): Unsupported date format: ${BUILD_AVOIDANCE_DATE_FORMAT}"; return 1;;
+        esac
+
+        # consume remaing non-interpreted content
+        if [ "$(echo "${DATE:0:${#x}}" |  tr ' ' '#')" != "${x}" ]; then
+            >&2 echo "$FUNCNAME (${LINENO}): Unexpected content '${DATE:0:${#x}}' does not match expected '${x}': '$1' being parsed vs '${BUILD_AVOIDANCE_DATE_FORMAT}'"
+            return 1
+        fi
+        DATE=${DATE:${#x}}
+    done
+
+    if [ "${DAY_OF_YEAR}" != "" ]; then
+        local YEAR_SEC
+        local DOY_SEC
+        YEAR_SEC="$(date -d "${CENTURY}${YEAR_IN_CENTURY}-01-01" '+%s')"
+        DOY_SEC=$((YEAR_SEC+(DAY_OF_YEAR-1)*24*60*60))
+        MONTH="$(date "@$DOY_SEC" "+%m")"
+        DAY="$(date "@$DOY_SEC" "+%d")"
+    fi
+
+    echo "${CENTURY}${YEAR_IN_CENTURY}-${MONTH}-${DAY}"
+    return 0
+}
+
+time_to_iso_8601 () {
+    TIME="$1"
+    local HOUR="00"
+    local H12=""
+    local AMPM=""
+    local MINUTE="00"
+    local SECOND="00"
+
+    CENTURY="$(date  '+%C')"
+
+    for x in $(echo "${BUILD_AVOIDANCE_TIME_FORMAT}" | tr ' ' '#' | sed 's/%%/#/g' | tr '%' ' ' ); do
+        # Consume format case options
+        case ${x:0:1} in
+            ^) x=${x:1};;
+            \#) x=${x:1};;
+            *) ;;
+        esac
+
+        # Process format
+        case $x in
+            H*)  HOUR=${TIME:0:2}; TIME=${TIME:2}; x=${x:1};;
+            0H*) HOUR=${TIME:0:2}; TIME=${TIME:2}; x=${x:2};;
+            _H*) HOUR="$(echo "${TIME:0:2}" | tr ' ' '0')"; TIME=${TIME:2}; x=${x:2};;
+            k*)  HOUR="$(echo "${TIME:0:2}" | tr ' ' '0')"; TIME=${TIME:2}; x=${x:1};;
+            0k*) HOUR=${TIME:0:2}; TIME=${TIME:2}; x=${x:2};;
+            _k*) HOUR="$(echo "${TIME:0:2}" | tr ' ' '0')"; TIME=${TIME:2}; x=${x:2};;
+
+            I*)  H12=${TIME:0:2}; TIME=${TIME:2}; x=${x:1};;
+            0I*) H12=${TIME:0:2}; TIME=${TIME:2}; x=${x:2};;
+            _I*) H12="$(echo "${TIME:0:2}" | tr ' ' '0')"; TIME=${TIME:2}; x=${x:2};;
+            l*)  H12="$(echo "${TIME:0:2}" | tr ' ' '0')"; TIME=${TIME:2}; x=${x:1};;
+            0l*) H12=${TIME:0:2}; TIME=${TIME:2}; x=${x:2};;
+            _l*) H12="$(echo "${TIME:0:2}" | tr ' ' '0')"; TIME=${TIME:2}; x=${x:2};;
+            p*) AMPM=${TIME:0:2}; TIME=${TIME:2}; x=${x:1};;
+
+            M*)  MINUTE=${TIME:0:2}; TIME=${TIME:2}; x=${x:1};;
+            0M*) MINUTE=${TIME:0:2}; TIME=${TIME:2}; x=${x:2};;
+            _M*) MINUTE="$(echo "${TIME:0:2}" | tr ' ' '0')"; TIME=${TIME:2}; x=${x:2};;
+
+            S*)  SECOND=${TIME:0:2}; TIME=${TIME:2}; x=${x:1};;
+            0S*) SECOND=${TIME:0:2}; TIME=${TIME:2}; x=${x:2};;
+            _S*) SECOND="$(echo "${TIME:0:2}" | tr ' ' '0')"; TIME=${TIME:2}; x=${x:2};;
+
+            R*) HOUR=${TIME:0:2}; MINUTE=${TIME:3:2} TIME=${TIME:5}; x=${x:1};;
+            r*) H12=${TIME:0:2}; MINUTE=${TIME:3:2}; SECOND=${TIME:6:2}; AMPM=${TIME:9:2}; TIME=${TIME:11}; x=${x:1};;
+            T*) HOUR=${TIME:0:2}; MINUTE=${TIME:3:2}; SECOND=${TIME:6:2}; TIME=${TIME:8}; x=${x:1};;
+
+            *) >&2 echo "$FUNCNAME (${LINENO}): Unsupported time format: ${BUILD_AVOIDANCE_TIME_FORMAT}"; return 1;;
+        esac
+
+        # consume remaing non-interpreted content
+        if [ "$(echo "${TIME:0:${#x}}" |  tr ' ' '#')" != "${x}" ]; then
+            >&2 echo "$FUNCNAME (${LINENO}): Unexpected content '${TIME:0:${#x}}' does not match expected '${x}': '$1' being parsed vs '${BUILD_AVOIDANCE_TIME_FORMAT}'"
+            return 1
+        fi
+        TIME=${TIME:${#x}}
+    done
+
+    if [ "$H12" != "" ] && [ "$AMPM" != "" ]; then
+        HOUR="$(date "$H12:01:01 $AMPM" '+%H')"
+    else
+        if [ "$H12" != "" ] && [ "$AMPM" != "" ]; then
+            >&2 echo "$FUNCNAME (${LINENO}): Unsupported time format: ${BUILD_AVOIDANCE_TIME_FORMAT}"
+            return 1
+        fi
+    fi
+
+    echo "${HOUR}:${MINUTE}:${SECOND}"
+    return 0
+}
+
+date_time_to_iso_8601 () {
+    local DATE_TIME="$1"
+    local DATE
+    local TIME
+    local DECODED_DATE
+    local DECODED_TIME
+    DATE=$(echo "${DATE_TIME}" | cut -d ${BUILD_AVOIDANCE_DATE_TIME_DELIM} -f 1)
+    TIME=$(echo "${DATE_TIME}" | cut -d ${BUILD_AVOIDANCE_DATE_TIME_DELIM} -f 2 | sed "s#${BUILD_AVOIDANCE_DATE_TIME_POSTFIX}\$##")
+    DECODED_DATE=$(date_to_iso_8601 "${DATE}")
+    DECODED_TIME=$(time_to_iso_8601 "${TIME}")
+    echo "${DECODED_DATE}T${DECODED_TIME}$(date $UTC '+%:z')"
+}
+
+#
+# test_build_avoidance_context <path-to-context-file>
+#
+# Is the provided context file compatible with the current
+# state of all of our gits?  A compatible context is one
+# where every commit in the context file is visible in our
+# current git history.
+#
+# Returns: Timestamp of context tested.
+# Exit code: 0 = Compatible
+#            1 = This context is older than the last applied
+#                build avoidance context.  If you are searching
+#                newest to oldest, you might as well stop.
+#            2 = Not compatible
+#
+test_build_avoidance_context () {
+    local context="$1"
+    local BA_LAST_SYNC_CONTEXT="$2"
+    local BA_CONTEXT=""
+
+    BA_CONTEXT=$(basename $context | cut -d '.' -f 1)
+    >&2 echo "test: $BA_CONTEXT"
+
+    if [ "$BA_CONTEXT" == "$BA_LAST_SYNC_CONTEXT" ]; then
+        # Stop the search.  We've reached the last sync point
+        BA_CONTEXT=""
+        echo "$BA_CONTEXT"
+        return 1
+    fi
+
+    git_test_context "$context"
+    result=$?
+    if [ $result -eq 0 ]; then
+        # found a new context !!!
+        echo "$BA_CONTEXT"
+        return 0
+    fi
+
+    # Continue the search
+    BA_CONTEXT=""
+    echo "$BA_CONTEXT"
+    return 2
+}
+
+
+#
+# get_build_avoidance_context
+#
+# Return URL of the most recent jenkins build that is compatable with
+# the current software context under $MY_REPO.
+#
+get_build_avoidance_context () {
+    (
+    local context
+    local BA_CONTEXT=""
+    local BA_LAST_SYNC_CONTEXT=""
+
+    # Load last synced context
+    if [ -f $BUILD_AVOIDANCE_LAST_SYNC_FILE ]; then
+        BA_LAST_SYNC_CONTEXT=$(head -n 1 $BUILD_AVOIDANCE_LAST_SYNC_FILE)
+    fi
+
+    mkdir -p $BUILD_AVOIDANCE_DATA_DIR
+    if [ $? -ne 0 ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): mkdir -p $BUILD_AVOIDANCE_DATA_DIR"
+        return 1
+    fi
+
+    local REMOTE_CTX_DIR="context"
+    local LOCAL_CTX_DIR="$BUILD_AVOIDANCE_DATA_DIR/context"
+
+    # First copy the directory containing all the context files for
+    # the reference builds.
+    >&2 echo "Download latest reference build contexts"
+
+    # Must set this prior to build_avoidance_copy_dir.
+    # The setting is not exported outside of the subshell.
+    BUILD_AVOIDANCE_URL="$BUILD_AVOIDANCE_HOST:$BUILD_AVOIDANCE_DIR"
+
+    build_avoidance_copy_dir "$REMOTE_CTX_DIR" "$LOCAL_CTX_DIR"
+    if [ $? -ne 0 ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): build_avoidance_copy_dir '$REMOTE_CTX_DIR' '$LOCAL_CTX_DIR'"
+        return 1
+    fi
+
+    # Search for a new context to sync
+    cd $MY_REPO
+
+    if [ "$BUILD_AVOIDANCE_DAY" == "" ]; then
+        # Normal case:
+        # Search all contexts, newest to oldest, for a good context.
+        for context in $(ls -1rd $LOCAL_CTX_DIR/*context); do
+            >&2 echo "context=$context"
+            BA_CONTEXT=$(test_build_avoidance_context $context $BA_LAST_SYNC_CONTEXT)
+            if [ $? -le 1 ]; then
+                # Stop search.  Might or might not have found a good context.
+                break;
+            fi
+        done
+    else
+        # Special case when a target day is specified.  Why would we do this?
+        # Reason is we might want the reference build to itself use build
+        # avoidance referencing prior builds of itself, except for one build
+        # a week when we use a full build rather than a build avoidance build.
+        #    e.g.   Sunday - full build
+        #           Mon-Sat - avoidance builds that refernce Sunday build.
+        #
+        # Starting from last <TARG_DAY> (e.g. "Sunday"), search newest to
+        # oldest for a good context.  If none found, increment the target
+        # day (e.g. Monday) and search again.  Keep incrementing until a
+        # good build is found, or target day + offset days would be a date
+        # in the furure.
+        #
+        local TARG_DAY=$BUILD_AVOIDANCE_DAY
+        local TODAY_DATE
+        local TODAY_DAY
+        local TARG_DATE=""
+        local TARG_TS
+        local TODAY_TS
+
+        TODAY_DATE=$(date  $UTC +%Y-%m-%d)
+        TODAY_DAY=$(date $UTC "+%A")
+
+        for OFFSET_DAYS in 0 1 2 3 4 5 6; do
+            if [ "$TARG_DAY" != "" ]; then
+                # Convert TARG_DAY+OFFSET_DAYS to TARG_DATE
+
+                if [ "$TODAY_DAY" == "$TARG_DAY" ]; then
+                    TARG_DATE=$(date $UTC -d"$TARG_DAY+$OFFSET_DAYS days" +%Y-%m-%d)
+                else
+                    TARG_DATE=$(date $UTC -d"last-$TARG_DAY+$OFFSET_DAYS days" +%Y-%m-%d)
+                fi
+                >&2 echo "TARG_DATE=$TARG_DATE"
+
+                TARG_TS=$(date $UTC -d "$TARG_DATE" +%s)
+                TODAY_TS=$(date $UTC -d "$TODAY_DATE" +%s)
+                if [ $TARG_TS -gt $TODAY_TS ]; then
+                    # Skip if offset has pushed us into future dates
+                    continue;
+                fi
+
+                if [ "$TARG_DATE" == "$TODAY_DATE" ]; then
+                    TARG_DATE=""
+                fi
+            fi
+
+            # Search build, newest to oldest, satisfying TARG_DATE
+            for f in $(ls -1rd $LOCAL_CTX_DIR/*context); do
+                DATE=$(date_to_iso_8601 $(basename "$f"))
+                if [ $? -ne 0 ]; then
+                    >&2 echo "Failed to extract date from filename '$(basename "$f")', ignoring file"
+                    continue
+                fi
+
+                >&2 echo "   DATE=$DATE, TARG_DATE=$TARG_DATE"
+
+                if [ "$DATE" == "$TARG_DATE" ] || [ "$TARG_DATE" == "" ] ; then
+                    context=$f;
+                else
+                    continue
+                fi
+
+                >&2 echo "context=$context"
+
+                BA_CONTEXT=$(test_build_avoidance_context $context $BA_LAST_SYNC_CONTEXT)
+
+                if [ $? -le 1 ]; then
+                    # Stop search.  Might or might not have found a good context.
+                    break;
+                fi
+            done
+
+            if [ "$BA_CONTEXT" != "" ]; then
+                # Found a good context.
+                break
+            fi
+        done
+    fi
+
+    if [ "$BA_CONTEXT" == "" ]; then
+        # No new context found
+        return 1
+    fi
+
+    # test that the reference build context hasn't been deleted
+    local BA_CONTEXT_DIR="$BUILD_AVOIDANCE_DIR/$BA_CONTEXT"
+    >&2 echo "ssh $BUILD_AVOIDANCE_HOST '[ -d $BA_CONTEXT_DIR ]'"
+    if ! ssh $BUILD_AVOIDANCE_HOST '[ -d $BA_CONTEXT_DIR ]' ; then
+        return 1
+    fi
+
+    # Save the latest context
+    >&2 echo "BA_CONTEXT=$BA_CONTEXT"
+    >&2 echo "BUILD_AVOIDANCE_LAST_SYNC_FILE=$BUILD_AVOIDANCE_LAST_SYNC_FILE"
+    echo $BA_CONTEXT > $BUILD_AVOIDANCE_LAST_SYNC_FILE
+
+    # The location of the load with the most compatable new context
+    URL=$BUILD_AVOIDANCE_HOST:$BA_CONTEXT_DIR
+
+    # return URL to caller.
+    echo $URL
+    return 0
+    )
+}
+
+
+#
+# build_avoidance_pre_clean <build-type>
+#
+# A place for any cleanup actions that must preceed a build avoidance build.
+#
+build_avoidance_pre_clean () {
+    local BUILD_TYPE="$1"
+
+    if [ "$BUILD_TYPE" == "" ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): BUILD_TYPE required"
+        return 1
+    fi
+
+    # clean prior builds
+    if [ -d $MY_WORKSPACE/$BUILD_TYPE ]; then
+        build-pkgs --clean --$BUILD_TYPE --no-build-avoidance
+        if [ $? -ne 0 ]; then
+            return 1
+        fi
+    fi
+
+    for f in $BUILD_AVOIDANCE_SRPM_FILES $BUILD_AVOIDANCE_RPM_FILES; do
+        if [ -f $MY_WORKSPACE/$BUILD_TYPE/$f ]; then
+            \rm -f $MY_WORKSPACE/$BUILD_TYPE/$f
+            if [ $? -ne 0 ]; then
+                >&2 echo "Error: $FUNCNAME (${LINENO}): rm -f $MY_WORKSPACE/$BUILD_TYPE/$f"
+                return 1
+            fi
+        fi
+    done
+
+    for d in $BUILD_AVOIDANCE_SRPM_DIRECTORIES $BUILD_AVOIDANCE_RPM_DIRECTORIES; do
+
+        if [ -d $MY_WORKSPACE/$BUILD_TYPE/$d ]; then
+            \rm -rf $MY_WORKSPACE/$BUILD_TYPE/$d
+            if [ $? -ne 0 ]; then
+                >&2 echo "Error: $FUNCNAME (${LINENO}): rm -rf $MY_WORKSPACE/$BUILD_TYPE/$d"
+                return 1
+            fi
+        fi
+    done
+
+    return 0
+}
+
+
+#
+# build_avoidance_copy_dir_rsync <remote-dir-path-rel> <local-dir-path> ['verbose']
+#
+# Copy a file from $BUILD_AVOIDANCE_URL/<remote-dir-path-rel>
+# to <local-dir-path> using rsync.
+#
+build_avoidance_copy_dir_rsync () {
+    local FROM="$1"
+    local TO="$2"
+    local VERBOSE="$3"
+    local FLAGS="-a -u"
+
+    if [ "$BUILD_AVOIDANCE_URL" == "" ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): BUILD_AVOIDANCE_URL no set"
+        return 1
+    fi
+    if [ "$VERBOSE" != "" ]; then
+        FLAGS="$FLAGS -v"
+        echo "rsync $FLAGS '$BUILD_AVOIDANCE_URL/$FROM/*' '$TO/'"
+    fi
+    rsync $FLAGS "$BUILD_AVOIDANCE_URL/$FROM/*" "$TO/"
+    return $?
+}
+
+#
+# build_avoidance_copy_file_rsync <remote-file-path-rel> <local-file-path> ['verbose']
+#
+# Copy a file from $BUILD_AVOIDANCE_URL/<remote-file-path-rel>
+# to <local-file-path> using rsync.
+#
+build_avoidance_copy_file_rsync () {
+    local FROM="$1"
+    local TO="$2"
+    local VERBOSE="$3"
+    local FLAGS="-a -u"
+
+    if [ "$BUILD_AVOIDANCE_URL" == "" ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): BUILD_AVOIDANCE_URL no set"
+        return 1
+    fi
+    if [ "$VERBOSE" != "" ]; then
+        FLAGS="$FLAGS -v"
+        echo "rsync $FLAGS '$BUILD_AVOIDANCE_URL/$FROM' '$TO'"
+    fi
+    rsync $FLAGS "$BUILD_AVOIDANCE_URL/$FROM" "$TO"
+    return $?
+}
+
+#
+# build_avoidance_copy_dir <remote-dir-path-rel> <local-dir-path> ['verbose']
+#
+# Copy a file from $BUILD_AVOIDANCE_URL/<remote-dir-path-rel>
+# to <local-dir-path>.  The copy method will be determined by
+# BUILD_AVOIDANCE_FILE_TRANSFER.  Only 'rsync' is supported at present.
+#
+# <local-dir-path> should be a directory,
+# mkdir -p will be called on <local-file-path>.
+#
+build_avoidance_copy_dir () {
+    local FROM="$1"
+    local TO="$2"
+    local VERBOSE="$3"
+
+    if [ "$VERBOSE" != "" ]; then
+        echo "mkdir -p '$TO'"
+    fi
+    mkdir -p "$TO"
+    if [ $? -ne 0 ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): mkdir -p $TO"
+        return 1
+    fi
+
+    case ${BUILD_AVOIDANCE_FILE_TRANSFER} in
+        rsync)
+            build_avoidance_copy_dir_rsync "$FROM" "$TO" "$VERBOSE"
+            return $?
+            ;;
+        *)
+            >&2 echo "Error: $FUNCNAME (${LINENO}): Unknown BUILD_AVOIDANCE_FILE_TRANSFER '${BUILD_AVOIDANCE_FILE_TRANSFER}'"
+            return 1
+            ;;
+    esac
+    return 1
+}
+
+#
+# build_avoidance_copy_file <remote-file-path-rel> <local-file-path> ['verbose']
+#
+# Copy a file from $BUILD_AVOIDANCE_URL/<remote-file-path-rel>
+# to <local-file-path>.  The copy method will be determined by
+# BUILD_AVOIDANCE_FILE_TRANSFER.  Only 'rsync' is supported at present.
+#
+# <local-file-path> should be a file, not a directory,
+# mkdir -p will be called on $(dirname <local-file-path>)
+#
+build_avoidance_copy_file () {
+    local FROM="$1"
+    local TO="$2"
+    local VERBOSE="$3"
+
+    if [ "$VERBOSE" != "" ]; then
+        echo "mkdir -p $(dirname '$TO')"
+    fi
+    mkdir -p "$(dirname "$TO")"
+    if [ $? -ne 0 ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): mkdir -p $(dirname "$TO")"
+        return 1
+    fi
+
+    case ${BUILD_AVOIDANCE_FILE_TRANSFER} in
+        rsync)
+            build_avoidance_copy_file_rsync "$FROM" "$TO" "$VERBOSE"
+            return $?
+            ;;
+        *)
+            >&2 echo "Error: $FUNCNAME (${LINENO}): Unknown BUILD_AVOIDANCE_FILE_TRANSFER '${BUILD_AVOIDANCE_FILE_TRANSFER}'"
+            return 1
+            ;;
+    esac
+    return 1
+}
+
+#
+# build_avoidance_copy <build-type> ['verbose']
+#
+# Copy the needed build artifacts for <build-type> from $BUILD_AVOIDANCE_URL.
+#
+build_avoidance_copy () {
+    local BUILD_TYPE="$1"
+    local VERBOSE="$2"
+
+    if [ "$BUILD_TYPE" == "" ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): BUILD_TYPE required"
+        return 1
+    fi
+
+    # Iterate through list of directories to copy
+    for d in $BUILD_AVOIDANCE_SRPM_DIRECTORIES $BUILD_AVOIDANCE_RPM_DIRECTORIES; do
+        build_avoidance_copy_dir "$BUILD_TYPE/$d" "$MY_WORKSPACE/$BUILD_TYPE/$d" "$VERBOSE"
+        if [ $? -ne 0 ]; then
+            >&2 echo "Error: $FUNCNAME (${LINENO}): build_avoidance_copy_dir '$BUILD_TYPE/$d' '$MY_WORKSPACE/$BUILD_TYPE/$d'"
+            return 1
+        fi
+    done
+
+    # Iterate through list of files to copy
+    for f in $BUILD_AVOIDANCE_SRPM_FILES $BUILD_AVOIDANCE_RPM_FILES; do
+        build_avoidance_copy_file "$BUILD_TYPE/$f" "$MY_WORKSPACE/$BUILD_TYPE/$f" "$VERBOSE"
+        if [ $? -ne 0 ]; then
+            >&2 echo "Error: $FUNCNAME (${LINENO}): build_avoidance_copy_file '$BUILD_TYPE/$f' '$MY_WORKSPACE/$BUILD_TYPE/$f'"
+            return 1
+        fi
+    done
+
+    return 0
+}
+
+#
+# build_avoidance_fixups <build-type>
+#
+# Fix paths in the build artifacts that we coppied that contain
+# the user name.
+#
+# Also, our credentials may differ from the reference build,
+# so substitute unsigned packages in place of signed packages.
+#
+build_avoidance_fixups () {
+    local BUILD_TYPE="$1"
+
+    local BA_SOURCE_BUILD_ENVIRONMENT
+    BA_SOURCE_BUILD_ENVIRONMENT="${BUILD_AVOIDANCE_USR}-$(basename $(dirname $BUILD_AVOIDANCE_URL))-$(basename $BUILD_AVOIDANCE_URL)-${SRC_BUILD_ENVIRONMENT}"
+    local RESULT_DIR=""
+    local FROM_DIR=""
+    local TO_DIR=""
+    local rpm_path_post_signing
+    local rpm_path_pre_signing
+    local rpm_name
+    local md5sum_post_signing
+    local md5sum_pre_signing
+
+    if [ "$BUILD_TYPE" == "" ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): BUILD_TYPE required"
+        return 1
+    fi
+
+    RESULT_DIR="$MY_WORKSPACE/$BUILD_TYPE/results"
+    FROM_DIR="${RESULT_DIR}/${BA_SOURCE_BUILD_ENVIRONMENT}-${BUILD_TYPE}"
+    TO_DIR="${RESULT_DIR}/${MY_BUILD_ENVIRONMENT}-${BUILD_TYPE}"
+    echo "$FUNCNAME: FROM_DIR=$FROM_DIR"
+    echo "$FUNCNAME: TO_DIR=$TO_DIR"
+    echo "$FUNCNAME: MY_BUILD_ENVIRONMENT=$MY_BUILD_ENVIRONMENT"
+
+    # Fix patchs the use MY_BUILD_ENVIRONMENT
+    if [ ! -d "$FROM_DIR" ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): Expected directory '$FROM_DIR' is missing."
+        return 1
+    fi
+
+    echo "$FUNCNAME: mv '$FROM_DIR' '$TO_DIR'"
+    \mv "$FROM_DIR" "$TO_DIR"
+    if [ $? -ne 0 ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): mv '$FROM_DIR' '$TO_DIR'"
+        return 1
+    fi
+
+    local MY_WS_BT="$MY_WORKSPACE/$BUILD_TYPE"
+
+    # Replace signed rpms with non-signed copies .... we aren't a formal build
+    for rpm_path_post_signing in $(find $MY_WS_BT/rpmbuild/RPMS -type f -name '*.rpm' | grep -v src.rpm); do
+
+        rpm_name=$(basename $rpm_path_post_signing)
+        rpm_path_pre_signing=$(find $MY_WS_BT/results -name $b | head -n1)
+        if [ "$rpm_path_pre_signing" != "" ]; then
+            md5sum_post_signing=$(md5sum ${rpm_path_post_signing} | cut -d ' ' -f 1)
+            md5sum_pre_signing=$(md5sum ${rpm_path_pre_signing} | cut -d ' ' -f 1)
+            if [ "${md5sum_post_signing}" != "${md5sum_pre_signing}" ]; then
+                echo "$FUNCNAME: fixing $rpm_name"
+                \rm -f ${rpm_path_post_signing}
+                if [ $? -ne 0 ]; then
+                    >&2 echo "Error: $FUNCNAME (${LINENO}): rm -f ${rpm_path_post_signing}"
+                    return 1
+                fi
+
+                \cp ${rpm_path_pre_signing} ${rpm_path_post_signing}
+                if [ $? -ne 0 ]; then
+                    >&2 echo "Error: $FUNCNAME (${LINENO}): cp ${rpm_path_pre_signing} ${rpm_path_post_signing}"
+                    return 1
+                fi
+            fi
+        fi;
+    done
+
+    return 0
+}
+
+
+#
+# build_avoidance <build-type>
+#
+# Look for a reference build that is applicable to our current git context.
+# and copy it to our local workspace, if we haven't already done so.
+#
+build_avoidance () {
+    local BUILD_TYPE="$1"
+
+    echo "==== Build Avoidance Start ===="
+
+    if [ "$BUILD_TYPE" == "" ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): BUILD_TYPE required"
+        return 1
+    fi
+
+    if [ "$BUILD_TYPE" == "installer" ]; then
+        >&2 echo "build_avoidance: BUILD_TYPE==installer not supported"
+        return 1
+    fi
+
+    build_avoidance_pre_clean $BUILD_TYPE
+    if [ $? -ne 0 ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): build_avoidance_pre_clean $BUILD_TYPE"
+        return 1
+    fi
+
+    build_avoidance_copy $BUILD_TYPE 'verbose'
+    if [ $? -ne 0 ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): build_avoidance_copy $BUILD_TYPE"
+        return 1
+    fi
+
+    build_avoidance_fixups $BUILD_TYPE
+    if [ $? -ne 0 ]; then
+        >&2 echo "Error: $FUNCNAME (${LINENO}): build_avoidance_fixups $BUILD_TYPE"
+        return 1
+    fi
+
+    echo "==== Build Avoidance Complete ===="
+    return 0
+}
+
+#
+# build_avoidance_save_reference_context
+#
+# For use by a reference build.  Copy the 'CONTEXT' file
+# from the build into a central directory where we save
+# the context of old builds.
+#
+# Individual reference builds use:
+#     MY_WORKSPACE=<common-dir>/<timestamp>
+# and context files are collected in dir:
+#     DEST_CTX_DIR=<common-dir>/context
+# using name:
+#     DEST_CTX=<timestamp>.context
+
+build_avoidance_save_reference_context () {
+    local DIR
+    DIR=$(dirname "${MY_WORKSPACE}")
+
+    # Note: SUB_DIR should be a timestamp
+    local SUB_DIR
+    SUB_DIR=$(basename "${MY_WORKSPACE}")
+
+    local SRC_CTX="${MY_WORKSPACE}/CONTEXT"
+    local DEST_CTX_DIR="${DIR}/context"
+    local DEST_CTX="${DEST_CTX_DIR}/${SUB_DIR}.context"
+
+    if [ ! -f "${SRC_CTX}" ]; then
+        echo "Context file not found at '${SRC_CTX}'"
+        return 1
+    fi
+
+    mkdir -p "${DEST_CTX_DIR}"
+    if [ $? -ne 0 ]; then
+        echo "Error: $FUNCNAME (${LINENO}): Failed to create directory '${DEST_CTX_DIR}'"
+        return 1
+    fi
+
+    cp "${SRC_CTX}" "${DEST_CTX}"
+    if [ $? -ne 0 ]; then
+        echo "Error: $FUNCNAME (${LINENO}): Failed to copy ${SRC_CTX} -> ${DEST_CTX}"
+        return 1
+    fi
+
+    return 0
+}
diff --git a/build-tools/build-pkgs b/build-tools/build-pkgs
index 9def3b01..15f7dd93 100755
--- a/build-tools/build-pkgs
+++ b/build-tools/build-pkgs
@@ -6,6 +6,9 @@
 # SPDX-License-Identifier: Apache-2.0
 #
 
+#
+# Build first src.rpms, then rpms, from source, or from a downloaded tarball
+# or src.rpm plus our additional patches.
 #
 # This program is a wrapper around build-pkgs-parallel and build-pkgs-serial
 #
diff --git a/build-tools/build-pkgs-parallel b/build-tools/build-pkgs-parallel
index 02360ac0..7d7bb2cc 100755
--- a/build-tools/build-pkgs-parallel
+++ b/build-tools/build-pkgs-parallel
@@ -1,10 +1,22 @@
 #!/bin/bash
 
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+#
+# Build first src.rpms, then rpms, from source, or from a downloaded tarball
+# or src.rpm plus our additional patches.
+#
 # This program is a wrapper around build-srpms-parallel and build-rpms-parallel
+#
 
 BUILD_PKGS_PARALLEL_DIR="$(dirname "$(readlink -f "${BASH_SOURCE[0]}" )" )"
 
 source "${BUILD_PKGS_PARALLEL_DIR}/git-utils.sh"
+source "${BUILD_PKGS_PARALLEL_DIR}/build-avoidance-utils.sh"
 source "${BUILD_PKGS_PARALLEL_DIR}/spec-utils"
 
 
@@ -13,14 +25,15 @@ usage () {
     echo "Usage: "
     echo "   Create source and Binary rpms:"
     echo "   Build optimizations (--no-descendants, --no-required, --no-build-info,"
-    echo "   --no-autoclean) are not recommended for the first build after a clone/pull,"
-    echo "   nor the final build prior to creating an iso or patch, but can be used"
-    echo "   for intermediate builds.  i.e. while debugging compilation failures." 
-    echo "      build-pkgs-parallel [--no-descendants] [--no-required] [--no-build-info] [--no-autoclean] [--careful] [--formal] [ list of package names ]"
+    echo "   --no-autoclean, --no-build-avoidance) are not recommended for the first build"
+    echo "   after a clone/pull, nor the final build prior to creating an iso or patch,"
+    echo "   but can be used for intermediate builds."
+    echo "   i.e. while debugging compilation failures."
+    echo "      build-pkgs-parallel [--build-avoidance | --no-build-avoidance] [--no-descendants] [--no-required] [--no-build-info] [--no-autoclean] [--careful] [--formal] [ list of package names ]"
     echo ""
     echo "   Delete source rpms, and the directories associated with it's creation:"
     echo "   Note: does not clean an edit environment"
-    echo "      build-pkgs-parallel --clean [ list of package names ]"
+    echo "      build-pkgs-parallel --clean [--build-avoidance | --no-build-avoidance] [ list of package names ]"
     echo ""
     echo "   Extract an src.rpm into a pair of git trees to aid in editing it's contents,"
     echo "   one for source code and one for metadata such as the spec file."
@@ -39,15 +52,20 @@ usage () {
 HELP=0
 CLEAN_FLAG=0
 EDIT_FLAG=0
+APPEND_LOG_FLAG=0
+BUILD_AVOIDANCE_FLAG=0
 STD_BUILD=1
 RT_BUILD=1
 INSTALLER_BUILD=0
 
+export BUILD_AVOIDANCE_URL=""
+
+
 # read the options
-TEMP=$(getopt -o h --long parallel,rt,std,installer,edit,no-meta-patch,no-descendants,no-required,no-build-info,no-autoclean,formal,careful,help,clean -n 'build-pkgs-parallel' -- "$@")
+TEMP=$(getopt -o h --long parallel,rt,std,installer,edit,build-avoidance,no-build-avoidance,build-avoidance-dir:,build-avoidance-host:,build-avoidance-user:,build-avoidance-day:,no-meta-patch,no-descendants,no-required,no-build-info,no-autoclean,formal,careful,help,clean,append-log -n 'build-pkgs-parallel' -- "$@")
 if [ $? -ne 0 ]; then
     usage
-    exit 0
+    exit 1
 fi
 eval set -- "$TEMP"
 
@@ -55,8 +73,21 @@ eval set -- "$TEMP"
 EXTRA_ARGS_COMMON=""
 EXTRA_ARGS_SRPM=""
 EXTRA_ARGS_RPM=""
+
+export BUILD_AVOIDANCE_OVERRIDE_DIR=""
+export BUILD_AVOIDANCE_OVERRIDE_HOST=""
+export BUILD_AVOIDANCE_OVERRIDE_USR=""
+export BUILD_AVOIDANCE_DAY=""
+
 while true ; do
     case "$1" in
+        --append-log)     APPEND_LOG_FLAG=1 ; shift ;;
+        --build-avoidance) BUILD_AVOIDANCE_FLAG=1 ; shift ;;
+        --no-build-avoidance) BUILD_AVOIDANCE_FLAG=0 ; shift ;;
+        --build-avoidance-dir)  BUILD_AVOIDANCE_OVERRIDE_DIR=$2; shift 2 ;;
+        --build-avoidance-host)  BUILD_AVOIDANCE_OVERRIDE_HOST=$2; shift 2 ;;
+        --build-avoidance-user)  BUILD_AVOIDANCE_OVERRIDE_USR=$2; shift 2 ;;
+        --build-avoidance-day) BUILD_AVOIDANCE_DAY=$2; shift 2 ;;
         --no-descendants) EXTRA_ARGS_COMMON+=" --no-descendants" ; shift ;;
         --formal)         EXTRA_ARGS_COMMON+=" --formal" ; shift ;;
         --careful)        EXTRA_ARGS_RPM+=" --careful" ; shift ;;
@@ -125,11 +156,15 @@ trap my_sighup HUP
 trap my_sigabrt ABRT
 trap my_sigterm TERM
 
+# Note: For ease of parsing, a TARGETS list always begins and ends 
+# with a space.  An empty target list consistes of two spaces.
 TARGETS=" $@ "
-TARGETS_STD=" "
-TARGETS_RT=" "
-TARGETS_INSTALLER=" "
-TARGETS_MISC=" "
+EMPTY_TARGETS="  "
+
+TARGETS_STD="$EMPTY_TARGETS"
+TARGETS_RT="$EMPTY_TARGETS"
+TARGETS_INSTALLER="$EMPTY_TARGETS"
+TARGETS_MISC="$EMPTY_TARGETS"
 
 find_targets () {
    local centos_pkg_dirs=$1
@@ -199,14 +234,28 @@ find_targets () {
       fi
    done
 
-   echo "$RESULT"
+   if [ "$RESULT" == " " ]; then
+       echo "$EMPTY_LIST"
+   else
+       echo "$RESULT"
+   fi
    return 0
 }
 
+if [ $EDIT_FLAG -eq 1 ] || [ "$TARGETS" != "$EMPTY_TARGETS" ]; then
+   BUILD_AVOIDANCE_FLAG=0
+fi
+
+echo "BUILD_AVOIDANCE_FLAG=$BUILD_AVOIDANCE_FLAG"
 echo "CLEAN_FLAG=$CLEAN_FLAG"
 echo "EDIT_FLAG=$EDIT_FLAG"
 
-if [ "x$TARGETS" != "x  " ]; then
+if [ $BUILD_AVOIDANCE_FLAG -eq 1 ]; then
+    # Build Avoidance requested. Get URL of a usable context, if any.
+    export BUILD_AVOIDANCE_URL=$(get_build_avoidance_context)
+fi
+
+if [ "$TARGETS" != "$EMPTY_TARGETS" ]; then
    TARGETS_STD="$(find_targets centos_pkg_dirs)"
 
    BUILD_TYPE_SAVE="$BUILD_TYPE"
@@ -247,44 +296,50 @@ echo "EXTRA_ARGS_RPM='$EXTRA_ARGS_RPM'"
 echo "TARGETS='$TARGETS'"
 echo "TARGETS_STD='$TARGETS_STD'"
 echo "TARGETS_RT='$TARGETS_RT'"
+echo "TARGETS_INSTALLER='$TARGETS_INSTALLER'"
 echo "TARGETS_MISC='$TARGETS_MISC'"
 
 if [ $CLEAN_FLAG -eq 1 ]; then
+
+   if [ "$TARGETS" == "$EMPTY_TARGETS" ] && [ $BUILD_AVOIDANCE_FLAG -eq 1 ] ; then
+      build_avoidance_clean
+   fi
+
    if [ $STD_BUILD -eq 1 ]; then
-      if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_STD" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_STD" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
          if [ $EDIT_FLAG -ne 1 ]; then
             echo "${BUILD_PKGS_PARALLEL_DIR}/build-rpms-parallel --std --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_STD $TARGETS_MISC"
             ${BUILD_PKGS_PARALLEL_DIR}/build-rpms-parallel --std --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_STD $TARGETS_MISC || exit 1
 
          fi
       fi
-      if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_STD" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_STD" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
          echo "${BUILD_PKGS_PARALLEL_DIR}/build-srpms-parallel --std --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_STD $TARGETS_MISC"
          ${BUILD_PKGS_PARALLEL_DIR}/build-srpms-parallel --std --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_STD $TARGETS_MISC || exit 1
       fi
    fi
 
    if [ $RT_BUILD -eq 1 ]; then
-      if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_RT" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_RT" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
          if [ $EDIT_FLAG -ne 1 ]; then
             echo "${BUILD_PKGS_PARALLEL_DIR}/build-rpms-parallel --rt --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_RT $TARGETS_MISC"
             ${BUILD_PKGS_PARALLEL_DIR}/build-rpms-parallel --rt --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_RT $TARGETS_MISC || exit 1
          fi
       fi
-      if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_RT" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_RT" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
          echo "${BUILD_PKGS_PARALLEL_DIR}/build-srpms-parallel --rt --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_RT $TARGETS_MISC"
          ${BUILD_PKGS_PARALLEL_DIR}/build-srpms-parallel --rt --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_RT $TARGETS_MISC || exit 1
       fi
    fi
 
    if [ $INSTALLER_BUILD -eq 1 ]; then
-      if [ "x$TARGETS" == "x" ] || [ "$TARGETS_INSTALLER" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_INSTALLER" != "$EMPTY_TARGETS" ]; then
          if [ $EDIT_FLAG -ne 1 ]; then
             echo "${BUILD_PKGS_PARALLEL_DIR}/build-rpms-serial --installer --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_INSTALLER"
             ${BUILD_PKGS_PARALLEL_DIR}/build-rpms-serial --installer --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_INSTALLER || exit 1
          fi
       fi
-      if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_INSTALLER" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_INSTALLER" != "$EMPTY_TARGETS" ]; then
          echo "${BUILD_PKGS_PARALLEL_DIR}/build-srpms-serial --installer --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_INSTALLER"
          ${BUILD_PKGS_PARALLEL_DIR}/build-srpms-serial --installer --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_INSTALLER || exit 1
       fi
@@ -317,13 +372,22 @@ function launch_build()
    fi
 
    echo "Launching $build_type build, logging to $logfile"
-   \rm $logfile
+   if [ $APPEND_LOG_FLAG -eq 0 ] && [ -f $logfile ]; then
+       \rm $logfile
+   fi
+
 
    echo -e "\n######## $(date): Launching build-srpms-parallel --$build_type $EXTRA_ARGS $@\n" | tee --append $logfile
+
+   echo "BUILD_AVOIDANCE_URL=$BUILD_AVOIDANCE_URL" | tee --append $logfile
+   if [ "x$BUILD_AVOIDANCE_URL" != "x" ]; then
+      echo "build_avoidance $build_type" | tee --append $logfile
+      build_avoidance $build_type 2>&1 | tee --append $logfile
+   fi
+
    # No clean flag, call build-srpms-parallel followed by build-rpms-parallel
    echo "${BUILD_PKGS_PARALLEL_DIR}/build-srpms-parallel --$build_type $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $targets" | tee --append $logfile
    ${BUILD_PKGS_PARALLEL_DIR}/build-srpms-parallel --$build_type $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $targets 2>&1 | tee --append $logfile
-
    rc=${PIPESTATUS[0]}
    if [ $rc -eq 0 ]; then
       echo -e "\n######## $(date): build-srpm-parallel --$build_type was successful" | tee --append $logfile
@@ -371,19 +435,18 @@ fi
 echo "Capture build context"
 git_context > "${MY_WORKSPACE}/CONTEXT"
 
-
 if [ $STD_BUILD -eq 1 ]; then
-   if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_STD" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+   if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_STD" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
       launch_build std
    else
-      echo "Skipping 'std' build, no valid targets in list: $TARGETS"
+      echo "Skipping 'std' build, no valid targets in list: '$TARGETS'"
    fi
 else
    echo "Skipping 'std' build"
 fi
 
 if [ $RT_BUILD -eq 1 ]; then
-   if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_RT" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+   if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_RT" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
       launch_build rt
    else
       echo "Skipping 'rt' build, no valid targets in list: $TARGETS"
@@ -393,7 +456,7 @@ else
 fi
 
 if [ $INSTALLER_BUILD -eq 1 ]; then
-   if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_INSTALLER" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+   if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_INSTALLER" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
       launch_build installer
    else
       echo "Skipping 'installer' build, no valid targets in list: $TARGETS"
@@ -402,6 +465,15 @@ else
    echo "Skipping 'installer' build"
 fi
 
+# Make sure REFERENCE_BUILD is set to something
+if [ -z $REFERENCE_BUILD ]; then
+    REFERENCE_BUILD=0
+fi
+
+if [ $REFERENCE_BUILD -eq 1 ]; then
+    echo "Saving reference context"
+    build_avoidance_save_reference_context
+fi
 
 echo "All builds were successful"
 
diff --git a/build-tools/build-pkgs-serial b/build-tools/build-pkgs-serial
index a0061d59..103ef537 100755
--- a/build-tools/build-pkgs-serial
+++ b/build-tools/build-pkgs-serial
@@ -1,10 +1,22 @@
 #!/bin/bash
 
-# This program is a wrapper around build-srpms and build-rpms
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+#
+# Build first src.rpms, then rpms, from source, or from a downloaded tarball
+# or src.rpm plus our additional patches.
+#
+# This program is a wrapper around build-srpms-serial and build-rpms-serial
+#
 
 BUILD_PKGS_SERIAL_DIR="$(dirname "$(readlink -f "${BASH_SOURCE[0]}" )" )"
 
 source "${BUILD_PKGS_SERIAL_DIR}/git-utils.sh"
+source "${BUILD_PKGS_SERIAL_DIR}/build-avoidance-utils.sh"
 source "${BUILD_PKGS_SERIAL_DIR}/spec-utils"
 
 
@@ -13,14 +25,15 @@ usage () {
     echo "Usage: "
     echo "   Create source and Binary rpms:"
     echo "   Build optimizations (--no-descendants, --no-required, --no-build-info,"
-    echo "   --no-autoclean) are not recommended for the first build after a clone/pull,"
-    echo "   nor the final build prior to creating an iso or patch, but can be used"
-    echo "   for intermediate builds.  i.e. while debugging compilation failures." 
-    echo "      build-pkgs-serial [--no-descendants] [--no-required] [--no-build-info] [--no-autoclean] [--careful] [--formal] [ list of package names ]"
+    echo "   --no-autoclean, --no-build-avoidance) are not recommended for the first build"
+    echo "   after a clone/pull, nor the final build prior to creating an iso or patch,"
+    echo "   but can be used for intermediate builds."
+    echo "   i.e. while debugging compilation failures."
+    echo "      build-pkgs-serial [--build-avoidance | --no-build-avoidance] [--no-descendants] [--no-required] [--no-build-info] [--no-autoclean] [--careful] [--formal] [ list of package names ]"
     echo ""
     echo "   Delete source rpms, and the directories associated with it's creation:"
     echo "   Note: does not clean an edit environment"
-    echo "      build-pkgs-serial --clean [ list of package names ]"
+    echo "      build-pkgs-serial --clean [--build-avoidance | --no-build-avoidance] [ list of package names ]"
     echo ""
     echo "   Extract an src.rpm into a pair of git trees to aid in editing it's contents,"
     echo "   one for source code and one for metadata such as the spec file."
@@ -39,12 +52,17 @@ usage () {
 HELP=0
 CLEAN_FLAG=0
 EDIT_FLAG=0
+APPEND_LOG_FLAG=0
+BUILD_AVOIDANCE_FLAG=0
 STD_BUILD=1
 RT_BUILD=1
 INSTALLER_BUILD=0
 
+export BUILD_AVOIDANCE_URL=""
+
+
 # read the options
-TEMP=$(getopt -o h --long serial,rt,std,edit,no-meta-patch,no-descendants,no-required,no-build-info,no-autoclean,formal,careful,help,clean -n 'build-pkgs' -- "$@")
+TEMP=$(getopt -o h --long serial,rt,std,installer,edit,build-avoidance,no-build-avoidance,build-avoidance-dir:,build-avoidance-host:,build-avoidance-user:,build-avoidance-day:,no-meta-patch,no-descendants,no-required,no-build-info,no-autoclean,formal,careful,help,clean,append-log -n 'build-pkgs-serial' -- "$@")
 if [ $? -ne 0 ]; then
     usage
     exit 1
@@ -55,8 +73,21 @@ eval set -- "$TEMP"
 EXTRA_ARGS_COMMON=""
 EXTRA_ARGS_SRPM=""
 EXTRA_ARGS_RPM=""
+
+export BUILD_AVOIDANCE_OVERRIDE_DIR=""
+export BUILD_AVOIDANCE_OVERRIDE_HOST=""
+export BUILD_AVOIDANCE_OVERRIDE_USR=""
+export BUILD_AVOIDANCE_DAY=""
+
 while true ; do
     case "$1" in
+        --append-log)     APPEND_LOG_FLAG=1 ; shift ;;
+        --build-avoidance) BUILD_AVOIDANCE_FLAG=1 ; shift ;;
+        --no-build-avoidance) BUILD_AVOIDANCE_FLAG=0 ; shift ;;
+        --build-avoidance-dir)  BUILD_AVOIDANCE_OVERRIDE_DIR=$2; shift 2 ;;
+        --build-avoidance-host)  BUILD_AVOIDANCE_OVERRIDE_HOST=$2; shift 2 ;;
+        --build-avoidance-user)  BUILD_AVOIDANCE_OVERRIDE_USR=$2; shift 2 ;;
+        --build-avoidance-day) BUILD_AVOIDANCE_DAY=$2; shift 2 ;;
         --no-descendants) EXTRA_ARGS_COMMON+=" --no-descendants" ; shift ;;
         --formal)         EXTRA_ARGS_COMMON+=" --formal" ; shift ;;
         --careful)        EXTRA_ARGS_RPM+=" --careful" ; shift ;;
@@ -81,11 +112,59 @@ if [ $HELP -eq 1 ]; then
     exit 0
 fi
 
+function my_exit() {
+    build-rpms-parallel --std --tmpfs-clean
+    build-rpms-parallel --rt --tmpfs-clean
+}
+
+function my_sigint() {
+    echo "build-pkgs-parallel sigint"
+    pkill -SIGABRT -P $BASHPID &> /dev/null
+    echo "build-pkgs-parallel waiting"
+    wait
+    echo "build-pkgs-parallel wait complete"
+
+}
+
+function my_sighup() {
+    echo "build-pkgs-parallel sighup"
+    pkill -SIGABRT -P $BASHPID &> /dev/null
+    echo "build-pkgs-parallel waiting"
+    wait
+    echo "build-pkgs-parallel wait complete"
+}
+
+function my_sigabrt() {
+    echo "build-pkgs-parallel sigabrt"
+    pkill -SIGABRT -P $BASHPID &> /dev/null
+    echo "build-pkgs-parallel waiting"
+    wait
+    echo "build-pkgs-parallel wait complete"
+}
+
+function my_sigterm() {
+    echo "build-pkgs-parallel sigterm"
+    pkill -SIGABRT -P $BASHPID &> /dev/null
+    echo "build-pkgs-parallel waiting"
+    wait
+    echo "build-pkgs-parallel wait complete"
+}
+
+trap my_exit EXIT
+trap my_sigint INT
+trap my_sighup HUP
+trap my_sigabrt ABRT
+trap my_sigterm TERM
+
+# Note: For ease of parsing, a TARGETS list always begins and ends 
+# with a space.  An empty target list consistes of two spaces.
 TARGETS=" $@ "
-TARGETS_STD=" "
-TARGETS_RT=" "
-TARGETS_INSTALLER=" "
-TARGETS_MISC=" "
+EMPTY_TARGETS="  "
+
+TARGETS_STD="$EMPTY_TARGETS"
+TARGETS_RT="$EMPTY_TARGETS"
+TARGETS_INSTALLER="$EMPTY_TARGETS"
+TARGETS_MISC="$EMPTY_TARGETS"
 
 find_targets () {
    local centos_pkg_dirs=$1
@@ -155,14 +234,28 @@ find_targets () {
       fi
    done
 
-   echo "$RESULT"
+   if [ "$RESULT" == " " ]; then
+       echo "$EMPTY_LIST"
+   else
+       echo "$RESULT"
+   fi
    return 0
 }
 
+if [ $EDIT_FLAG -eq 1 ] || [ "$TARGETS" != "$EMPTY_TARGETS" ]; then
+   BUILD_AVOIDANCE_FLAG=0
+fi
+
+echo "BUILD_AVOIDANCE_FLAG=$BUILD_AVOIDANCE_FLAG"
 echo "CLEAN_FLAG=$CLEAN_FLAG"
 echo "EDIT_FLAG=$EDIT_FLAG"
 
-if [ "x$TARGETS" != "x  " ]; then
+if [ $BUILD_AVOIDANCE_FLAG -eq 1 ]; then
+    # Build Avoidance requested. Get URL of a usable context, if any.
+    export BUILD_AVOIDANCE_URL=$(get_build_avoidance_context)
+fi
+
+if [ "$TARGETS" != "$EMPTY_TARGETS" ]; then
    TARGETS_STD="$(find_targets centos_pkg_dirs)"
 
    BUILD_TYPE_SAVE="$BUILD_TYPE"
@@ -207,45 +300,51 @@ echo "TARGETS_INSTALLER='$TARGETS_INSTALLER'"
 echo "TARGETS_MISC='$TARGETS_MISC'"
 
 if [ $CLEAN_FLAG -eq 1 ]; then
+
+   if [ "$TARGETS" == "$EMPTY_TARGETS" ] && [ $BUILD_AVOIDANCE_FLAG -eq 1 ] ; then
+      build_avoidance_clean
+   fi
+
    if [ $STD_BUILD -eq 1 ]; then
-      if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_STD" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_STD" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
          if [ $EDIT_FLAG -ne 1 ]; then
             echo "${BUILD_PKGS_SERIAL_DIR}/build-rpms-serial --std --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_STD $TARGETS_MISC"
             ${BUILD_PKGS_SERIAL_DIR}/build-rpms-serial --std --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_STD $TARGETS_MISC || exit 1
 
          fi
       fi
-      if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_STD" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_STD" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
          echo "${BUILD_PKGS_SERIAL_DIR}/build-srpms-serial --std --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_STD $TARGETS_MISC"
          ${BUILD_PKGS_SERIAL_DIR}/build-srpms-serial --std --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_STD $TARGETS_MISC || exit 1
       fi
    fi
 
    if [ $RT_BUILD -eq 1 ]; then
-      if [ "x$TARGETS" == "x" ] || [ "$TARGETS_RT" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_RT" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
          if [ $EDIT_FLAG -ne 1 ]; then
             echo "${BUILD_PKGS_SERIAL_DIR}/build-rpms-serial --rt --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_RT $TARGETS_MISC"
             ${BUILD_PKGS_SERIAL_DIR}/build-rpms-serial --rt --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_RT $TARGETS_MISC || exit 1
          fi
       fi
-      if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_RT" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_RT" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
          echo "${BUILD_PKGS_SERIAL_DIR}/build-srpms-serial --rt --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_RT $TARGETS_MISC"
          ${BUILD_PKGS_SERIAL_DIR}/build-srpms-serial --rt --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_RT $TARGETS_MISC || exit 1
       fi
    fi
 
    if [ $INSTALLER_BUILD -eq 1 ]; then
-      if [ "x$TARGETS" == "x" ] || [ "$TARGETS_INSTALLER" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_INSTALLER" != "$EMPTY_TARGETS" ]; then
          if [ $EDIT_FLAG -ne 1 ]; then
             echo "${BUILD_PKGS_SERIAL_DIR}/build-rpms-serial --installer --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_INSTALLER"
             ${BUILD_PKGS_SERIAL_DIR}/build-rpms-serial --installer --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_RPM $TARGETS_INSTALLER || exit 1
          fi
       fi
-      if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_INSTALLER" != " " ]; then
+      if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_INSTALLER" != "$EMPTY_TARGETS" ]; then
          echo "${BUILD_PKGS_SERIAL_DIR}/build-srpms-serial --installer --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_INSTALLER"
          ${BUILD_PKGS_SERIAL_DIR}/build-srpms-serial --installer --clean $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $TARGETS_INSTALLER || exit 1
       fi
    fi
+
    exit $?
 fi
 
@@ -273,8 +372,18 @@ function launch_build()
    fi
 
    echo "Launching $build_type build, logging to $logfile"
+   if [ $APPEND_LOG_FLAG -eq 0 ] && [ -f $logfile ]; then
+       \rm $logfile
+   fi
 
    echo -e "\n######## $(date): Launching build-srpms-serial --$build_type $EXTRA_ARGS $@\n" | tee --append $logfile
+
+   echo "BUILD_AVOIDANCE_URL=$BUILD_AVOIDANCE_URL" | tee --append $logfile
+   if [ "x$BUILD_AVOIDANCE_URL" != "x" ]; then
+      echo "build_avoidance $build_type" | tee --append $logfile
+      build_avoidance $build_type 2>&1 | tee --append $logfile
+   fi
+
    # No clean flag, call build-srpms-serial followed by build-rpms-serial
    echo "${BUILD_PKGS_SERIAL_DIR}/build-srpms-serial --$build_type $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $targets" | tee --append $logfile
    ${BUILD_PKGS_SERIAL_DIR}/build-srpms-serial --$build_type $EXTRA_ARGS_COMMON $EXTRA_ARGS_SRPM $targets 2>&1 | tee --append $logfile
@@ -326,7 +435,7 @@ echo "Capture build context"
 git_context > "${MY_WORKSPACE}/CONTEXT"
 
 if [ $STD_BUILD -eq 1 ]; then
-   if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_STD" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+   if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_STD" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
       launch_build std
    else
       echo "Skipping 'std' build, no valid targets in list: $TARGETS"
@@ -336,7 +445,7 @@ else
 fi
 
 if [ $RT_BUILD -eq 1 ]; then
-   if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_RT" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+   if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_RT" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
       launch_build rt
    else
       echo "Skipping 'rt' build, no valid targets in list: $TARGETS"
@@ -346,7 +455,7 @@ else
 fi
 
 if [ $INSTALLER_BUILD -eq 1 ]; then
-   if [ "x$TARGETS" == "x  " ] || [ "$TARGETS_INSTALLER" != " " ] || [ "$TARGETS_MISC" != " " ]; then
+   if [ "$TARGETS" == "$EMPTY_TARGETS" ] || [ "$TARGETS_INSTALLER" != "$EMPTY_TARGETS" ] || [ "$TARGETS_MISC" != "$EMPTY_TARGETS" ]; then
       launch_build installer
    else
       echo "Skipping 'installer' build, no valid targets in list: $TARGETS"
@@ -355,6 +464,16 @@ else
    echo "Skipping 'installer' build"
 fi
 
+# Make sure REFERENCE_BUILD is set to something
+if [ -z $REFERENCE_BUILD ]; then
+    REFERENCE_BUILD=0
+fi
+
+if [ $REFERENCE_BUILD -eq 1 ]; then
+    echo "Saving reference context"
+    build_avoidance_save_reference_context
+fi
+
 echo "All builds were successful"
 
 exit 0
diff --git a/build-tools/build-rpms b/build-tools/build-rpms
index 937c406a..1867743e 100755
--- a/build-tools/build-rpms
+++ b/build-tools/build-rpms
@@ -1,6 +1,16 @@
 #!/bin/bash
 
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+#
+# Builds rpm files from src.rpm files.
+#
 # This program is a wrapper around build-rpms-parallel and build-rpms-serial
+#
 
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
diff --git a/build-tools/build-rpms-parallel b/build-tools/build-rpms-parallel
index 17234913..f56e9782 100755
--- a/build-tools/build-rpms-parallel
+++ b/build-tools/build-rpms-parallel
@@ -6,6 +6,24 @@
 # SPDX-License-Identifier: Apache-2.0
 #
 
+#
+# Builds rpm files from src.rpm files.
+#
+# This version compiles packages in parrallel if sufficient resources
+# (cpu's and memory) are available.
+#
+# The location of packages to be built is
+# $MY_WORKSPACE/<build-type>/rpmbuild/SRPMS.
+#
+# The build order is a derived from the BuildRequires in the 
+# spec files in the src.rpms.  Note that the BuildRequires sometimes
+# create dependency loops, so no correct order can be computed.  In these
+# cases we add a retry loop.  As long as one new package builds, we
+# keep retrying the loop, until all are built, or no progress is made.
+# So please don't panic and CTRL-C just because you see a few error
+# messages go by!
+#
+
 
 export ME=$(basename "$0")
 CMDLINE="$ME $@"
@@ -122,12 +140,10 @@ create-no-clean-list () {
    if [ ! -f $NO_CLEAN_LIST_FILE ]; then
        NEED_REBUILD=1
    else
-       if [ -f MY_BUILD_CFG ]; then
-           if [ -f MY_BUILD_CFG ]; then
-               find "$MY_BUILD_CFG" -not -newermm "$NO_CLEAN_LIST_FILE" | grep -q $(basename $MY_BUILD_CFG)
-               if [ $? -eq 0 ]; then
-                   NEED_REBUILD=1
-               fi
+       if [ -f $MY_BUILD_CFG ]; then
+           find "$MY_BUILD_CFG" -not -newermm "$NO_CLEAN_LIST_FILE" | grep -q $(basename $MY_BUILD_CFG)
+           if [ $? -eq 0 ]; then
+               NEED_REBUILD=1
            fi
        fi
    fi
diff --git a/build-tools/build-rpms-serial b/build-tools/build-rpms-serial
index 77cece6f..6358e586 100755
--- a/build-tools/build-rpms-serial
+++ b/build-tools/build-rpms-serial
@@ -6,6 +6,22 @@
 # SPDX-License-Identifier: Apache-2.0
 #
 
+# 
+# Builds rpm files from src.rpm files.
+#
+# This version compiles one package at a time.
+# 
+# The location of packages to be built is 
+# $MY_WORKSPACE/<build-type>/rpmbuild/SRPMS.
+#
+# The build order is a derived from the BuildRequires in the 
+# spec files in the src.rpms.  Note that the BuildRequires sometimes
+# create dependency loops, so no correct order can be computed.  In these
+# cases we add a retry loop.  As long as one new package builds, we
+# keep retrying the loop, until all are built, or no progress is made.
+# So please don't panic and CTRL-C just because you see a few error
+# messages go by!
+#
 
 export ME=$(basename "$0")
 CMDLINE="$ME $@"
@@ -63,12 +79,10 @@ create-no-clean-list () {
    if [ ! -f $NO_CLEAN_LIST_FILE ]; then
        NEED_REBUILD=1
    else
-       if [ -f MY_BUILD_CFG ]; then
-           if [ -f MY_BUILD_CFG ]; then
-               find "$MY_BUILD_CFG" -not -newermm "$NO_CLEAN_LIST_FILE" | grep -q $(basename $MY_BUILD_CFG)
-               if [ $? -eq 0 ]; then
-                   NEED_REBUILD=1
-               fi
+       if [ -f $MY_BUILD_CFG ]; then
+           find "$MY_BUILD_CFG" -not -newermm "$NO_CLEAN_LIST_FILE" | grep -q $(basename $MY_BUILD_CFG)
+           if [ $? -eq 0 ]; then
+               NEED_REBUILD=1
            fi
        fi
    fi
diff --git a/build-tools/build-srpms b/build-tools/build-srpms
index aef8a681..c0f1bafc 100755
--- a/build-tools/build-srpms
+++ b/build-tools/build-srpms
@@ -1,6 +1,24 @@
 #!/bin/bash
 
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+#
+# Create src.rpm files from source, or from a downloaded tarball
+# or src.rpm plus our additional patches.
+#
 # This program is a wrapper around build-srpms-parallel and build-srpms-serial
+#
+# The location of packages to be build are identified by
+# <distro>_pkg_dirs[_<opt-build-type>] files located at the root of
+# any git tree (e.g. istx/stx-integ/centos_pkg_dirs).
+#
+# The build of an individual package is driven by its build_srpm.data
+# file plus a <pkg-name>.spec file or an srpm_path file.
+#
 
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
diff --git a/build-tools/build-srpms-common.sh b/build-tools/build-srpms-common.sh
new file mode 100644
index 00000000..2afce635
--- /dev/null
+++ b/build-tools/build-srpms-common.sh
@@ -0,0 +1,187 @@
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+#
+# Functions common to build-srpm-serial and build-srpm-parallel.
+#
+
+SRC_BUILD_TYPE_SRPM="srpm"
+SRC_BUILD_TYPE_SPEC="spec"
+SRC_BUILD_TYPES="$SRC_BUILD_TYPE_SRPM $SRC_BUILD_TYPE_SPEC"
+
+
+str_lst_contains() {
+    TARGET="$1"
+    LST="$2"
+
+    if [[ $LST =~ (^|[[:space:]])$TARGET($|[[:space:]]) ]] ; then
+        return 0
+    else
+        return 1
+    fi
+}
+
+
+#
+# capture_md5sum_from_input_vars <src-build-type> <srpm-or-spec-path> <work-dir>
+#
+# Returns md5 data for all input files of a src.rpm.
+# Assumes PKG_BASE, ORIG_SRPM_PATH have been defined and the
+# build_srpm.data file has already been sourced.
+#
+# Arguments:
+#   src-build-type: Any single value from $SRC_BUILD_TYPES.
+#                   e.g. 'srpm' or 'spec'
+#   srpm-or-spec-path: Absolute path to an src.rpm, or to a
+#                      spec file.
+#   work-dir: Optional working directory.  If a path is
+#             specified but does not exist, it will be created.
+#
+# Returns: output of md5sum command with canonical path names
+#
+md5sums_from_input_vars () {
+    local SRC_BUILD_TYPE="$1"
+    local SRPM_OR_SPEC_PATH="$2"
+    local WORK_DIR="$3"
+
+    local TMP_FLAG=0
+    local LINK_FILTER='[/]stx[/]downloads[/]'
+
+    if ! str_lst_contains "$SRC_BUILD_TYPE" "$SRC_BUILD_TYPES" ; then
+        >&2  echo "ERROR: $FUNCNAME (${LINENO}): invalid arg: SRC_BUILD_TYPE='$SRC_BUILD_TYPE'"
+        return 1
+    fi
+
+    if [ -z $WORK_DIR ]; then
+        WORK_DIR=$(mktemp -d /tmp/${FUNCNAME}_XXXXXX)
+        if [ $? -ne 0 ]; then
+            >&2  echo "ERROR: $FUNCNAME (${LINENO}): mktemp -d /tmp/${FUNCNAME}_XXXXXX"
+            return 1
+        fi
+        TMP_FLAG=1
+    else
+        mkdir -p "$WORK_DIR"
+        if [ $? -ne 0 ]; then
+            >&2  echo "ERROR: $FUNCNAME (${LINENO}): mkdir -p '$WORK_DIR'"
+            return 1
+        fi
+    fi
+
+    local INPUT_FILES="$WORK_DIR/srpm_input.files"
+    local INPUT_LINKS="$WORK_DIR/srpm_input.links"
+    local INPUT_FILES_SORTED="$WORK_DIR/srpm_sorted_input.files"
+
+    if [ -f "$INPUT_LINKS" ]; then
+        \rm -f "$INPUT_LINKS"
+    fi
+
+    # Create lists of input files (INPUT_FILES) and symlinks (INPUT_LINKS).
+    # First elements are absolute paths...
+    find "$PKG_BASE" -type f > $INPUT_FILES
+    if [ $? -ne 0 ]; then
+        >&2  echo "ERROR: $FUNCNAME (${LINENO}): find '$PKG_BASE' -type f"
+        return 1
+    fi
+
+    if [ "$SRC_BUILD_TYPE" == "$SRC_BUILD_TYPE_SRPM" ]; then
+        find "$SRPM_OR_SPEC_PATH" -type f >> $INPUT_FILES
+        if [ $? -ne 0 ]; then
+            >&2  echo "ERROR: $FUNCNAME (${LINENO}): find '$SRPM_OR_SPEC_PATH' -type f"
+            return 1
+        fi
+    fi
+
+    # ...additional elements are based on values already sourced from
+    # build_srpm.data (COPY_LIST, SRC_DIR, COPY_LIST_TO_TAR, OPT_DEP_LIST)
+    # and may be relative to $PKG_BASE
+    #
+    # Use a subshell so any directory changes have no lastin effect.
+    (
+        cd $PKG_BASE
+        if [ "x$COPY_LIST" != "x" ]; then
+            ABS_COPY_LIST=$(readlink -f $COPY_LIST)
+            if [ $? -ne 0 ]; then
+                >&2  echo "ERROR: $FUNCNAME (${LINENO}): readlink -f '$COPY_LIST' -type f"
+                return 1
+            fi
+
+            find $ABS_COPY_LIST -type f >> $INPUT_FILES
+            if [ $? -ne 0 ]; then
+                >&2  echo "ERROR: $FUNCNAME (${LINENO}): find '$ABS_COPY_LIST' -type f"
+                return 1
+            fi
+
+            # Treat most links normally
+            find $ABS_COPY_LIST -type l | grep -v "$LINK_FILTER" >> $INPUT_FILES
+
+            # Links in the downloads directory likely point outside of $MY_REPO
+            # and might not be 'portable' from a build avoidance prespective.
+            # We'll treat these specially.
+            find $ABS_COPY_LIST -type l | grep "$LINK_FILTER" >> $INPUT_LINKS
+        fi
+
+        if [ "$SRC_BUILD_TYPE" == "$SRC_BUILD_TYPE_SPEC" ]; then
+            if [ "x$SRC_DIR" != "x" ]; then
+                if [ -d "$SRC_DIR" ]; then
+                    find $(readlink -f "$SRC_DIR") -type f | grep -v '[/][.]git$' | grep -v '[/][.]git[/]' >> $INPUT_FILES
+                    if [ $? -ne 0 ]; then
+                        >&2  echo "ERROR: $FUNCNAME (${LINENO}): find '$SRC_DIR' -type f"
+                        return 1
+                    fi
+                fi
+            fi
+
+            if [ "x$COPY_LIST_TO_TAR" != "x" ]; then
+                find $(readlink -f "$COPY_LIST_TO_TAR") -type f >> $INPUT_FILES
+                if [ $? -ne 0 ]; then
+                    >&2  echo "ERROR: $FUNCNAME (${LINENO}): find '$COPY_LIST_TO_TAR' -type f"
+                    return 1
+                fi
+            fi
+        fi
+
+        if [ "x$OPT_DEP_LIST" != "x" ]; then
+            find $(readlink -f "$OPT_DEP_LIST") -type f >> $INPUT_FILES 2> /dev/null
+            if [ $? -ne 0 ]; then
+                >&2  echo "ERROR: $FUNCNAME (${LINENO}): find '$OPT_DEP_LIST' -type f"
+                return 1
+            fi
+        fi
+    )
+    if [ $? -eq 1 ]; then
+        return -1
+    fi
+
+    # Create sorted, unique list of cononical paths
+    (
+        # Regular files, get canonical path
+        cat $INPUT_FILES | xargs readlink -f
+
+        # A Symlink that likely points outside of $MY_REPO.
+        # get canonical path to the symlink itself, and not
+        # to what the symlink points to.
+        if [ -f $INPUT_LINKS ]; then
+            while IFS= read -r f; do
+                echo "$(readlink -f $(dirname $f))/$(basename $f)"
+            done < "$INPUT_LINKS"
+        fi
+    ) | sort --unique > $INPUT_FILES_SORTED
+
+    # Remove $MY_REPO prefix from paths
+    cat $INPUT_FILES_SORTED | xargs md5sum | sed "s# $(readlink -f $MY_REPO)/# #"
+
+    if [ $TMP_FLAG -eq 0 ]; then
+        \rm -f $INPUT_FILES_SORTED
+        \rm -f $INPUT_FILES
+        if [ -f $INPUT_LINKS ]; then
+            \rm -f $INPUT_LINKS
+        fi
+    else
+        \rm -rf $WORK_DIR
+    fi
+
+    return 0
+}
diff --git a/build-tools/build-srpms-parallel b/build-tools/build-srpms-parallel
index 13fa4804..47e91e87 100755
--- a/build-tools/build-srpms-parallel
+++ b/build-tools/build-srpms-parallel
@@ -1,6 +1,26 @@
 #!/bin/bash
 # set -x
 
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+#
+# Create src.rpm files from source, or from a downloaded tarball
+# or src.rpm plus our additional patches.
+#
+# This version tries to compile many packages in parallel.
+#
+# The location of packages to be build are identified by
+# <distro>_pkg_dirs[_<opt-build-type>] files located at the root of
+# any git tree (e.g. stx/stx-integ/centos_pkg_dirs).
+#
+# The build of an individul package is driven by it's build_srpm.data
+# file plus a <pkg-name>.spec file or an srpm_path file.
+#
+
 export ME=$(basename "$0")
 CMDLINE="$ME $@"
 
@@ -9,6 +29,7 @@ source $BUILD_SRPMS_PARALLEL_DIR/git-utils.sh
 source $BUILD_SRPMS_PARALLEL_DIR/spec-utils
 source $BUILD_SRPMS_PARALLEL_DIR/srpm-utils
 source $BUILD_SRPMS_PARALLEL_DIR/classify
+source $BUILD_SRPMS_PARALLEL_DIR/build-srpms-common.sh
 
 
 INITIAL_DIR=$(pwd)
@@ -372,7 +393,7 @@ build_dir () {
          fi
 
          if [ "${ORIG_SRPM_PATH}x" == "x" ]; then
-            # handle mirror: definitions
+            # handle 3rd_party: definitions
             echo "$p" | grep "^3rd_party:" >/dev/null && ORIG_SRPM_PATH=$(echo $p | sed "s%^3rd_party:%$THIRD_PARTY_ROOT/%")
          fi
 
@@ -455,7 +476,7 @@ clean_srpm_dir () {
    local SRPM_OUT_NAME
    local INPUTS_TO_CLEAN=""
 
-   if [ $EXCLUDE_MD5 == "" ]; then
+   if [ "$EXCLUDE_MD5" == "" ]; then
        EXCLUDE_MD5=0
    fi
 
@@ -626,24 +647,15 @@ build_dir_srpm () {
       # Capture md5 data for all input files
       #
       local TARGET_SOURCES_DIR="$SOURCES_DIR/$TARGET_FOUND"
-      local INPUT_FILES="$TARGET_SOURCES_DIR/srpm_input.files"
-      local INPUT_FILES_SORTED="$TARGET_SOURCES_DIR/srpm_sorted_input.files"
       local INPUT_FILES_MD5="$TARGET_SOURCES_DIR/srpm_input.md5"
       local REFERENCE_MD5="$TARGET_SOURCES_DIR/srpm_reference.md5"
 
       mkdir -p "$TARGET_SOURCES_DIR"
-      find $PKG_BASE -type f > $INPUT_FILES
-      find $ORIG_SRPM_PATH -type f >> $INPUT_FILES
-         (
-         cd $PKG_BASE
-         if [ "x$COPY_LIST" != "x" ]; then
-            find $COPY_LIST -type f >> $INPUT_FILES
-         fi
-         )
-      cat $INPUT_FILES | xargs readlink -f | sort --unique > $INPUT_FILES_SORTED
-      \rm -f $INPUT_FILES
-      cat $INPUT_FILES_SORTED | xargs md5sum | sed "s# $(readlink -f $MY_REPO)/# #" > $INPUT_FILES_MD5
-      \rm -f $INPUT_FILES_SORTED
+      md5sums_from_input_vars "$SRC_BUILD_TYPE_SRPM" "$ORIG_SRPM_PATH" "$TARGET_SOURCES_DIR" > "$INPUT_FILES_MD5"
+      if [ $? -ne 0 ]; then
+         echo "ERROR: $FUNCNAME (${LINENO}): md5sums_from_input_vars '$SRC_BUILD_TYPE_SRPM' '$ORIG_SRPM_PATH' '$TARGET_SOURCES_DIR'"
+         return 1
+      fi
       echo "Wrote: $INPUT_FILES_MD5"
 
       #
@@ -946,38 +958,15 @@ build_dir_spec () {
          # Capture md5 data for all input files
          #
          local TARGET_SOURCES_DIR="$SOURCES_DIR/$TARGET_FOUND"
-         local INPUT_FILES="$TARGET_SOURCES_DIR/srpm_input.files"
-         local INPUT_FILES_SORTED="$TARGET_SOURCES_DIR/srpm_sorted_input.files"
          local INPUT_FILES_MD5="$TARGET_SOURCES_DIR/srpm_input.md5"
          local REFERENCE_MD5="$TARGET_SOURCES_DIR/srpm_reference.md5"
 
          mkdir -p "$TARGET_SOURCES_DIR"
-         find $PKG_BASE -type f > $INPUT_FILES
-         find $ORIG_SRPM_PATH -type f >> $INPUT_FILES
-            (
-            cd $PKG_BASE
-            if [ "x$SRC_DIR" != "x" ]; then
-               if [ -d "$SRC_DIR" ]; then
-                  find $SRC_DIR -type f | grep -v '[/][.]git$' | grep -v '[/][.]git[/]' >> $INPUT_FILES
-               fi
-            fi
-
-            if [ "x$COPY_LIST" != "x" ]; then
-               find $COPY_LIST -type f >> $INPUT_FILES
-            fi
-
-            if [ "x$COPY_LIST_TO_TAR" != "x" ]; then
-               find $COPY_LIST_TO_TAR -type f >> $INPUT_FILES
-            fi
-
-            if [ "x$OPT_DEP_LIST" != "x" ]; then
-               find $OPT_DEP_LIST -type f >> $INPUT_FILES 2> /dev/null
-            fi
-            )
-         cat $INPUT_FILES | xargs readlink -f | sort --unique > $INPUT_FILES_SORTED
-         \rm -f $INPUT_FILES
-         cat $INPUT_FILES_SORTED | xargs md5sum | sed "s# $(readlink -f $MY_REPO)/# #" > $INPUT_FILES_MD5
-         \rm -f $INPUT_FILES_SORTED
+         md5sums_from_input_vars "$SRC_BUILD_TYPE_SPEC" "$SPEC" "$TARGET_SOURCES_DIR" > "$INPUT_FILES_MD5"
+         if [ $? -ne 0 ]; then
+             echo "ERROR: $FUNCNAME (${LINENO}): md5sums_from_input_vars '$SRC_BUILD_TYPE_SPEC' '$SPEC' '$TARGET_SOURCES_DIR'"
+             return 1
+         fi
          echo "Wrote: $INPUT_FILES_MD5"
 
          #
diff --git a/build-tools/build-srpms-serial b/build-tools/build-srpms-serial
index 4398115b..fbdd33cb 100755
--- a/build-tools/build-srpms-serial
+++ b/build-tools/build-srpms-serial
@@ -1,6 +1,26 @@
 #!/bin/bash
 # set -x
 
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+#
+# Create src.rpm files from source, or from a downloaded tarball
+# or src.rpm plus our additional patches.
+#
+# This version only tries to compile on package at a time.
+#
+# The location of packages to be build are identified by
+# <distro>_pkg_dirs[_<opt-build-type>] files located at the root of
+# any git tree (e.g. stx/stx-integ/centos_pkg_dirs).
+#
+# The build of an individul package is driven by it's build_srpm.data
+# file plus a <pkg-name>.spec file or an srpm_path file.
+#
+
 export ME=$(basename "$0")
 CMDLINE="$ME $@"
 
@@ -10,6 +30,7 @@ source $BUILD_SRPMS_SERIAL_DIR/git-utils.sh
 source $BUILD_SRPMS_SERIAL_DIR/spec-utils
 source $BUILD_SRPMS_SERIAL_DIR/srpm-utils
 source $BUILD_SRPMS_SERIAL_DIR/classify
+source $BUILD_SRPMS_PARALLEL_DIR/build-srpms-common.sh
 
 
 INITIAL_DIR=$(pwd)
@@ -438,7 +459,7 @@ clean_srpm_dir () {
    local SRPM_OUT_NAME
    local INPUTS_TO_CLEAN=""
 
-   if [ $EXCLUDE_MD5 == "" ]; then
+   if [ "$EXCLUDE_MD5" == "" ]; then
        EXCLUDE_MD5=0
    fi
 
@@ -603,24 +624,15 @@ build_dir_srpm () {
       # Capture md5 data for all input files
       #
       local TARGET_SOURCES_DIR="$SOURCES_DIR/$TARGET_FOUND"
-      local INPUT_FILES="$TARGET_SOURCES_DIR/srpm_input.files"
-      local INPUT_FILES_SORTED="$TARGET_SOURCES_DIR/srpm_sorted_input.files"
       local INPUT_FILES_MD5="$TARGET_SOURCES_DIR/srpm_input.md5"
       local REFERENCE_MD5="$TARGET_SOURCES_DIR/srpm_reference.md5"
 
       mkdir -p "$TARGET_SOURCES_DIR"
-      find $PKG_BASE -type f > $INPUT_FILES
-      find $ORIG_SRPM_PATH -type f >> $INPUT_FILES
-         (
-         cd $PKG_BASE
-         if [ "x$COPY_LIST" != "x" ]; then
-            find $COPY_LIST -type f >> $INPUT_FILES
-         fi
-         )
-      cat $INPUT_FILES | xargs readlink -f | sort --unique > $INPUT_FILES_SORTED
-      \rm -f $INPUT_FILES
-      cat $INPUT_FILES_SORTED | xargs md5sum | sed "s# $(readlink -f $MY_REPO)/# #" > $INPUT_FILES_MD5
-      \rm -f $INPUT_FILES_SORTED
+      md5sums_from_input_vars "$SRC_BUILD_TYPE_SRPM" "$ORIG_SRPM_PATH" "$TARGET_SOURCES_DIR" > "$INPUT_FILES_MD5"
+      if [ $? -ne 0 ]; then
+         echo "ERROR: $FUNCNAME (${LINENO}): md5sums_from_input_vars '$SRC_BUILD_TYPE_SRPM' '$ORIG_SRPM_PATH' '$TARGET_SOURCES_DIR'"
+         return 1
+      fi
       echo "Wrote: $INPUT_FILES_MD5"
 
       #
@@ -922,38 +934,15 @@ build_dir_spec () {
          # Capture md5 data for all input files
          #
          local TARGET_SOURCES_DIR="$SOURCES_DIR/$TARGET_FOUND"
-         local INPUT_FILES="$TARGET_SOURCES_DIR/srpm_input.files"
-         local INPUT_FILES_SORTED="$TARGET_SOURCES_DIR/srpm_sorted_input.files"
          local INPUT_FILES_MD5="$TARGET_SOURCES_DIR/srpm_input.md5"
          local REFERENCE_MD5="$TARGET_SOURCES_DIR/srpm_reference.md5"
 
          mkdir -p "$TARGET_SOURCES_DIR"
-         find $PKG_BASE -type f > $INPUT_FILES
-         find $ORIG_SRPM_PATH -type f >> $INPUT_FILES
-            (
-            cd $PKG_BASE
-            if [ "x$SRC_DIR" != "x" ]; then
-               if [ -d "$SRC_DIR" ]; then
-                  find $SRC_DIR -type f | grep -v '[/][.]git$' | grep -v '[/][.]git[/]' >> $INPUT_FILES
-               fi
-            fi
-
-            if [ "x$COPY_LIST" != "x" ]; then
-               find $COPY_LIST -type f >> $INPUT_FILES
-            fi
-
-            if [ "x$COPY_LIST_TO_TAR" != "x" ]; then
-               find $COPY_LIST_TO_TAR -type f >> $INPUT_FILES
-            fi
-
-            if [ "x$OPT_DEP_LIST" != "x" ]; then
-               find $OPT_DEP_LIST -type f >> $INPUT_FILES 2> /dev/null
-            fi
-            )
-         cat $INPUT_FILES | xargs readlink -f | sort --unique > $INPUT_FILES_SORTED
-         \rm -f $INPUT_FILES
-         cat $INPUT_FILES_SORTED | xargs md5sum | sed "s# $(readlink -f $MY_REPO)/# #" > $INPUT_FILES_MD5
-         \rm -f $INPUT_FILES_SORTED
+         md5sums_from_input_vars "$SRC_BUILD_TYPE_SPEC" "$SPEC" "$TARGET_SOURCES_DIR" > "$INPUT_FILES_MD5"
+         if [ $? -ne 0 ]; then
+             echo "ERROR: $FUNCNAME (${LINENO}): md5sums_from_input_vars '$SRC_BUILD_TYPE_SPEC' '$SPEC' '$TARGET_SOURCES_DIR'"
+             return 1
+         fi
          echo "Wrote: $INPUT_FILES_MD5"
 
          #
diff --git a/build-tools/git-utils.sh b/build-tools/git-utils.sh
index 94490df1..de432464 100755
--- a/build-tools/git-utils.sh
+++ b/build-tools/git-utils.sh
@@ -9,6 +9,10 @@
 # by repo manifests.
 #
 
+git_ctx_root_dir () {
+    dirname "${MY_REPO}"
+}
+
 #
 # git_list <dir>:
 #      Return a list of git root directories found under <dir>
@@ -22,12 +26,12 @@ git_list () {
 
 # GIT_LIST: A list of root directories for all the gits under $MY_REPO/..
 #           as absolute paths.
-export GIT_LIST=$(git_list "$(dirname "${MY_REPO}")")
+export GIT_LIST=$(git_list "$(git_ctx_root_dir)")
 
 
 # GIT_LIST_REL: A list of root directories for all the gits under $MY_REPO/..
 #               as relative paths.
-export GIT_LIST_REL=$(for p in $GIT_LIST; do echo .${p#$(dirname ${MY_REPO})}; done)
+export GIT_LIST_REL=$(for p in $GIT_LIST; do echo .${p#$(git_ctx_root_dir)}; done)
 
 
 #
@@ -85,7 +89,9 @@ git_list_containing_tag () {
 
 git_context () {
     (
-    cd $MY_REPO
+    cd $(git_ctx_root_dir)
+
+    local d
     for d in $GIT_LIST_REL; do
         (
         cd ${d}
@@ -95,3 +101,48 @@ git_context () {
     done
     )
 }
+
+#
+# git_test_context <context>:
+#
+# Test if all commits referenced in the context are present
+# in the history of the gits in their current checkout state.
+#
+# Returns: 0 = context is present in git history
+#          1 = At least one element of context is not present
+#          2 = error
+#
+git_test_context () {
+    local context="$1"
+    local query=""
+    local target_hits=0
+    local actual_hits=0
+
+    if [ ! -f "$context" ]; then
+        return 2
+    fi
+
+    query=$(mktemp "/tmp/git_test_context_XXXXXX")
+    if [ "$query" == "" ]; then
+        return 2
+    fi
+
+    # Transform a checkout context into a query that prints
+    # all the commits that are found in the git history.
+    #
+    # Limit search to last 500 commits in the interest of speed.
+    # I don't expect to be using contexts more than a few weeks old.
+    cat "$context" | \
+        sed "s#checkout -f \([a-e0-9]*\)#rev-list --max-count=500 HEAD | \
+        grep \1#" > $query
+
+    target_hits=$(cat "$context" | wc -l)
+    actual_hits=$(cd $(git_ctx_root_dir); source $query | wc -l)
+    \rm $query
+
+    if [ $actual_hits -eq $target_hits ]; then
+        return 0
+    fi
+
+    return 1
+}
diff --git a/build-tools/sign-secure-boot b/build-tools/sign-secure-boot
index 4401e5cf..19a6c62f 100755
--- a/build-tools/sign-secure-boot
+++ b/build-tools/sign-secure-boot
@@ -1,5 +1,11 @@
 #!/bin/bash
 
+#
+# Copyright (c) 2018 Wind River Systems, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
 # This script calls into an external signing server to perform signing of some
 # packages in the system.  The old packages (which are typically generated by
 # the build system and signed by placeholder keys) are overwritten by the new
@@ -264,7 +270,7 @@ function rebuild_pkgs
 	fi
 
         echo "Performing rebuild of packages: $PKGS_TO_REBUILD"
-        FORMAL_BUILD=0 build-pkgs --no-descendants --no-build-info --no-required --careful $PKGS_TO_REBUILD > $LOGFILE 2>&1
+        FORMAL_BUILD=0 build-pkgs --no-descendants --no-build-info --no-required --careful --append-log $PKGS_TO_REBUILD > $LOGFILE 2>&1
 
 	if [ $? -ne 0 ]; then
 		echo "Could not rebuild packages: $PKGS_TO_REBUILD -- see $LOGFILE for details"