Add option to synthesize a consistent lkgr commit by running deps2git.py

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.
 
+force_branch=no
+quiet=no
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --force-branch)
+      force_branch=yes
+      ;;
+    -q|--quiet)
+      quiet=yes
+      ;;
+    *)
+      echo "Unknown option: $1"
+      ;;
+  esac
+  shift
+done
+
 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
@@ skipping 28 matching lines @@
 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
 
+# Pick a name for the new branch.  Use `git rev-parse` to make sure the branch
+# doesn't already exist; if it does, iterate an integer suffix to uniquify it.
+lkgr_branch="git_lkgr_r${svn_lkgr}"
+digit=1
+git rev-parse --verify -q "${lkgr_branch}" >/dev/null
+while [ $? -eq 0 ]; do
+  lkgr_branch="git_lkgr_r${svn_lkgr}_${digit}"
+  digit=`expr $digit + 1`
+  git rev-parse --verify -q "${lkgr_branch}" >/dev/null
+done
+
 if [ "${closest_svn_commit}" = "${git_lkgr}" ]; then
   echo "${closest_commit}"
+  if [ "$force_branch" = "yes" ]; then
+    git checkout -b "${lkgr_branch}" "${closest_commit}"
+  fi
   exit 0
-else
-  cat <<EOF 1>&2
+elif [ "${quiet}" = "yes" ]; then
+  exit 1
+elif [ "${force_branch}" = "no" ]; then
+  cat <<EOF
 There is no master commit which corresponds exactly to lkgr.
 The closest commit is ${closest_commit}.
 EOF
+  read -n 1 -p 'Would you like to create a new branch based on lkgr? (y/N) '
+  echo
+  if [ "x$REPLY" != "xy" -a "x$REPLY" != "xY" ]; then
+    exit 0
+  fi
+fi
+
+current_head=`git branch | grep '^\*' | cut -c3-`
+if [ "${current_head}" = "(no branch)" ]; then
+  current_head=`git rev-parse HEAD`
+fi
+
+git checkout --detach "${git_lkgr}" &&
+python tools/deps2git/deps2git.py -d DEPS -o .DEPS.git -w .. &&
+git add .DEPS.git &&
+python tools/deps2git/deps2submodules.py .DEPS.git &&
+git commit -m "SVN changes up to revision $svn_lkgr" &&
+git checkout -b "${lkgr_branch}" HEAD
+
+if [ $? != 0 ]; then
+  cat <<EOF
+
+--------------------------------------------------------------------------------
+Something went wrong!  Restoring your previous state by checking out
+$current_head
+
+Please file a bug report at http://new.crbug.com.
+--------------------------------------------------------------------------------
+
+EOF
+  git checkout --force $current_head
   exit 1
 fi
+
+cat <<EOF
+
+--------------------------------------------------------------------------------
+The new branch "$lkgr_branch" was branched from this commit:
+
+$git_lkgr
+
+... which maps to the svn lkgr commit r${svn_lkgr}.  The new branch
+has one additional commit, to bring .DEPS.git, .gitmodules, and the
+invisible git submodule files up to date with DEPS.
+
+To create a working branch, do this:
+
+\$ git branch --track my_new_branch $lkgr_branch
+
+'git-cl upload' will do the right thing, i.e., it will cherry-pick all
+your changes from my_new_branch, but *not* the .DEPS.git+.gitmodules+submodules
+commit on $lkgr_branch.
+--------------------------------------------------------------------------------
+
+EOF