git command to find a git revision corresponding to lkgr.

Review URL: https://chromiumcodereview.appspot.com/10958056

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@158892 0039d316-1c4b-4281-b951-d872f2087c98

git-lkgr

+#!/bin/bash
+
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+svn_lkgr=`curl -s http://chromium-status.appspot.com/lkgr`
+if [ $? != 0 -o -z "$svn_lkgr" ]; then
+  echo 'Could not get svn lkgr from chromium-status.appspot.com/lkgr'
+  exit 1
+fi
+
+# Run a trivial git-svn command to force it to update the revision cache
+# (which causes spew that might otherwise confuse the next command).
+git svn info > /dev/null
+if [ $? != 0 ]; then
+  cat <<EOF 1>&2
+Could not run a trivial git-svn command.  You probably need to set up your
+working directory for git-svn, by following these instructions:
+
+http://code.google.com/p/chromium/wiki/UsingNewGit#Initial_checkout
+EOF
+  exit 1
+fi
+
+git_lkgr=`git svn find-rev r${svn_lkgr}`
+if [ $? != 0 -o -z "$git_lkgr" ]; then
+  cat <<EOF 1>&2
+Could not map svn revision ${svn_lkgr} to a git commit.
+You may need to `git fetch` and try again.
+EOF
+  exit 1
+fi
+
+set -o pipefail
+closest_commit=`git rev-list --ancestry-path \
+    --grep='SVN changes up to revision [0-9]*' \
+    ${git_lkgr}..refs/remotes/origin/master | tail -1`
+if [ $? != 0 -o -z "$closest_commit" ]; then
+  cat <<EOF 1>&2
+Could not find a blessed git commit (with accurate .DEPS.git and submodules)
+after svn lkgr revision $svn_lkgr.
+EOF
+  exit 1
+fi
+
+closest_svn_commit=`git rev-list -n 1 ${closest_commit}^1`
+if [ $? != 0 -o -z "$closest_svn_commit" ]; then
+  cat <<EOF 1>&2
+I am thoroughly confused.  Please file a bug report at http://new.crbug.com.
+EOF
+  exit 1
+fi
+
+if [ "${closest_svn_commit}" = "${git_lkgr}" ]; then
+  echo "${closest_commit}"
+  exit 0
+else
+  cat <<EOF 1>&2
+There is no master commit which corresponds exactly to lkgr.
+The closest commit is ${closest_commit}.
+EOF
+  exit 1
+fi