git command to find a git revision corresponding to lkgr.

git-lkgr

+#!/bin/bash
+
+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
+
+git_lkgr=`git svn find-rev r${svn_lkgr}`

[Jeffrey Yasskin, 2012/09/22 00:16:06]

I'm guessing a `git svn fetch` before this line would prevent the "Partial
rebuilding" error and make it more likely that the revision is found. You should
probably do a `git fetch` before that to make it run quickly. Alternately, do
those inside this `if` to speed up the common case.

[szager1, 2012/09/22 00:54:48]

I'd prefer not run any `fetch` operations, to prevent any unintended side
effects.  I enhanced the error message to suggest running `git fetch`.  `git svn
fetch` will never do anything helpful for this script.

+if [ $? != 0 -o -z "$git_lkgr" ]; then
+  echo 'Could not map svn revision ${svn_lkgr} to a git commit.'
+  exit 1
+fi
+
+closest_commit=`git rev-list --ancestry-path --grep='SVN changes up to revision [0-9]*' ${git_lkgr}..refs/remotes/origin/master | tail -1`

[Jeffrey Yasskin, 2012/09/22 00:16:06]

set pipefail to make the exit status of this command match the `git` exit status
instead of the `tail` exit status.

[szager1, 2012/09/22 00:54:48]

Done.

+if [ $? != 0 -o -z "$closest_commit" ]; then
+  echo 'Could not find a blessed git commit (with accurate .DEPS.git and submodules) after lkgr'
+  exit 1
+fi
+
+closest_svn_commit=`git rev-list -n 1 ${closest_commit}^1`
+if [ $? != 0 -o -z "$closest_svn_commit" ]; then
+  echo 'I am thoroughly confused.  Please send a bug report to chrome-infrastructure-team.'
+  exit 1
+fi
+
+if [ "${closest_svn_commit}" = "${git_lkgr}" ]; then
+  echo "${closest_commit}"
+  exit 0
+else
+  echo "There is no master commit which corresponds exactly to lkgr." 1>&2
+  echo "The closest commit is ${closest_commit}." 1>&2
+  exit 1
+fi