#!/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