Create gerrit-cherry-pick for client usage

End users can now obtain the gerrit-cherry-pick script by fetching
it with scp:

  scp -P 29418 review.source.android.com:bin/gerrit-cherry-pick ~/bin

Arguments passed to the script represent changes or patch sets like
repo download would accept.  The script executes git fetch to ensure
the objects are available locally, then passes the changes through
git am to apply them to the current branch.

Common git am workflow is supported, including adding a new
Signed-off-by line for the caller, and fixing broken whitespace.

Later the cherry-picked changes can be automatically closed out
by uploading them back as replacement patch sets.

Signed-off-by: Shawn O. Pearce <sop@google.com>

2 files changed, 207 insertions, 0 deletions

diff --git a/src/main/java/com/google/gerrit/server/ssh/scproot/TOC b/src/main/java/com/google/gerrit/server/ssh/scproot/TOC
index e2c5dfac80..9200ff61a8 100644
--- a/src/main/java/com/google/gerrit/server/ssh/scproot/TOC
+++ b/src/main/java/com/google/gerrit/server/ssh/scproot/TOC
@@ -1,3 +1,4 @@
 # Format of this file is:
 #   mode <SPACE> fullpath
 #
+755 bin/gerrit-cherry-pick
diff --git a/src/main/java/com/google/gerrit/server/ssh/scproot/bin/gerrit-cherry-pick b/src/main/java/com/google/gerrit/server/ssh/scproot/bin/gerrit-cherry-pick
new file mode 100644
index 0000000000..ceddff8a01
--- /dev/null
+++ b/src/main/java/com/google/gerrit/server/ssh/scproot/bin/gerrit-cherry-pick
@@ -0,0 +1,206 @@
+#!/bin/sh
+#
+# Copyright (C) 2009 The Android Open Source Project
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+# http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# 
+
+usage() {
+  echo >&2 "usage: $0 remote changeid..."
+  echo >&2 "usage: $0 --continue"
+  echo >&2 "usage: $0 --skip"
+  echo >&2 "usage: $0 --abort"
+  echo >&2 "usage: $0 [--close|--replace] remote"
+  exit 1
+}
+
+die() {
+  echo >&2 "fatal: $1"
+  exit 1
+}
+
+GIT_DIR=$(git rev-parse --git-dir) || exit
+CL="$GIT_DIR/GERRIT_CHANGES"
+STATE="$GIT_DIR/rebase-gerrit"
+TODO="$STATE/todo"
+
+RESOLVEMSG="
+When you have resolved this problem run \"$0 --continue\".
+If you would prefer to skip this patch, run \"$0 --skip\".
+"
+
+pop_action() {
+  sed -e 1d <"$TODO" >>"$TODO".new
+  mv -f "$TODO".new "$TODO"
+}
+
+mark_done() {
+  read commit changeid <"$TODO"
+  changeid=$(get_changeid "$changeid")
+  head_after=$(git rev-parse HEAD^0)
+  head_before=$(cat "$STATE/head_before")
+  if ! test $head_after = $head_before
+  then
+    echo $head_after >"$CL/$changeid"
+  fi
+  pop_action
+}
+
+do_next() {
+  while test -s "$TODO"
+  do
+    read commit changeid <"$TODO"
+    git rev-parse HEAD^0 >"$STATE/head_before"
+    git format-patch \
+        -k --stdout --full-index --ignore-if-in-upstream \
+        $commit^..$commit |
+    git am $git_am_opt --rebasing --resolvemsg="$RESOLVEMSG" || exit
+    mark_done
+  done
+
+  echo >&2 "Done."
+  rm -rf "$STATE"
+}
+
+git_am_opt=
+if test -f "$STATE/git_am_opt"
+then
+  git_am_opt=$(cat "$STATE/git_am_opt")
+fi
+
+while test $# != 0
+do
+  case "$1" in
+  --continue)
+    test -f "$TODO" || die "No cherry-pick in progress?"
+    git am $git_am_opt --rebasing --resolvemsg="$RESOLVEMSG" --resolved || exit
+    mark_done
+    do_next
+    exit
+    ;;
+  --skip)
+    test -f "$TODO" || die "No cherry-pick in progress?"
+    git reset --hard HEAD || exit
+    git am --skip || exit
+    pop_action
+    do_next
+    exit
+    ;;
+  --abort)
+    test -f "$TODO" || die "No cherry-pick in progress?"
+    git reset --hard HEAD
+    git am --skip
+    rm -rf "$STATE"
+    ;;
+  --close|--replace)
+    shift
+    test -d "$CL" || die "No changes to close"
+    test $# = 1   || usage
+    remote=$1
+    printf %s "git push $remote" >&2
+    rs=$(cd "$CL" && for change_id in *; do
+      test "$change_id" = '*' && die "No changes to close"
+      c=$(cat "$change_id");
+      echo "$c:refs/changes/$change_id";
+      echo ' \' >&2;
+      printf %s "  $c:refs/changes/$change_id" >&2
+      done)
+    echo >&2
+    echo >&2
+    git push $remote $rs
+    rc=$?
+    test $rc = 0 && rm -rf "$CL"
+    exit $rc
+    ;;
+  --whitespace=*)
+    git_am_opt="$git_am_opt $1"
+    ;;
+  --committer-date-is-author-date|--ignore-date)
+    git_am_opt="$git_am_opt $1"
+    ;;
+  -C*)
+    git_am_opt="$git_am_opt $1"
+    ;;
+  -s|--signoff)
+    git_am_opt="$git_am_opt $1"
+    ;;
+  -*)
+    usage
+    ;;
+  *)
+    break
+    ;;
+  esac
+  shift
+done
+
+get_changeid() {
+  case $1 in
+  */*) echo ${1%%/*} ;;
+  *)   echo $1 ;;
+  esac
+}
+
+to_ref() {
+  case $1 in
+  */*)
+    change_id=${1%%/*}
+    patchset_id=${1##*/}
+    ;;
+  *)
+    change_id=$1
+    patchset_id=1
+    ;;
+  esac
+
+  hash=$(($change_id % 100))
+  case $hash in
+  [0-9]) hash="0$hash" ;;
+  esac
+
+  echo "refs/changes/$hash/$change_id/$patchset_id"
+}
+
+get_revid() {
+  grep $(to_ref $1) <"$GIT_DIR/FETCH_HEAD" | cut -f1
+}
+
+# Initialize state
+#
+test $# -lt 2 && usage
+remote="$1"
+shift
+
+mkdir "$STATE" || die "cherry-pick already in progress"
+echo $git_am_opt >"$STATE/git_am_opt"
+
+if ! git fetch $remote $(for id; do to_ref $id; done)
+then
+  rm -rf $STATE
+  exit 1
+fi
+
+(for id
+ do
+  if revid=$(get_revid $id)
+  then
+    echo "$revid $id"
+  else
+    echo >&2 "fatal: $id not found"
+    exit 1
+  fi
+done) >"$TODO"
+
+mkdir -p "$CL"
+echo >&2
+do_next