Update sync_google3.sh to match autoroller.py.

tools/sync_google3.sh

 #!/bin/bash
 # Copyright 2014 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Syncs //depot/google3/third_party/skia/HEAD to the latest revision of Skia.
 # If this script is not run from a Piper client, creates a new CitC client. Also
 # updates README.google.
 #
@@ skipping 12 matching lines @@
 if [ -z "${GOOGLE3}" ]; then
   CLIENT_NAME="sync_skia_$(date '+%F-%H-%M-%S')"
   ${MY_DIR}/create_skia_google3_client.sh "${CLIENT_NAME}"
   GOOGLE3="/google/src/cloud/${USER}/${CLIENT_NAME}/google3"
 fi
 cd "${GOOGLE3}/third_party/skia/HEAD"
 ${MY_DIR}/git_clone_to_google3.sh --skia_rev "${SKIA_REV}"
 
 echo "Synced client ${CLIENT_NAME} to ${SKIA_REV}"
 
+# Grab previous Git revision.
+GOOGLE3_REV="$(grep "Version: " README.google | cut -d ' ' -f 2)"
+
 # Update README.google.
 sed --in-place "s/^Version: .*/Version: ${SKIA_REV}/" README.google
-sed --in-place "s/URL: http:\/\/skia.googlesource.com\/skia\/+archive\/.*\.tar\.gz/URL: http:\/\/skia.googlesource.com\/skia\/+archive\/${SKIA_REV}.tar.gz/" README.google
-CURRENT_DATE=`date '+%d %B %Y'`
-echo "Updated using sync_google3.sh on $CURRENT_DATE by $USER@google.com" >> README.google
+sed --in-place "s/URL: https:\/\/skia.googlesource.com\/skia\/+archive\/.*\.tar\.gz/URL: https:\/\/skia.googlesource.com\/skia\/+archive\/${SKIA_REV}.tar.gz/" README.google
 
 # Add README.google to the default change.
 g4 reopen
+
+# Generate commit description.
+CURRENT_DATE=`date '+%d %B %Y'`
+COMMIT_RANGE="${GOOGLE3_REV:0:9}..${SKIA_REV:0:9}"
+CHANGES="$(git log ${COMMIT_RANGE} --date=short --no-merges --format='%ad %ae %s')"
+COMMITS="$(wc -l <<EOF
+${CHANGES}
+EOF
+)"
+DESC="$(cat <<EOF
+Roll Skia ${COMMIT_RANGE} (${COMMITS} commits)
+
+https://chromium.googlesource.com/skia.git/+log/${COMMIT_RANGE}
+
+$ git log ${COMMIT_RANGE} --date=short --no-merges --format='%ad %ae %s'
+${CHANGES}
+
+Change created by sync_google3.sh on ${CURRENT_DATE} by ${USER}
+EOF
+)"
+
 # Create a new CL.
-CHANGE="$(g4 change --desc "Update skia HEAD to ${SKIA_REV}.")"
+CHANGE="$(g4 change --desc "${DESC}.")"
 CL="$(echo "${CHANGE}" | sed "s/Change \([0-9]\+\) created.*/\1/")"
 
 echo "Created CL ${CL} (http://cl/${CL})"
 
 # Run presubmit (will run TAP tests).
 if g4 presubmit -c "${CL}"; then
   echo "CL is ready for review and submit at http://cl/${CL}"
 else
   echo "Presubmit failed for CL ${CL} in client ${CLIENT_NAME}" 1>&2
   exit 3
 fi