Update git-lkgr with --create and --name options.

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
+branch_name=""
+checkout_branch=no
+create_branch=no
 quiet=no
 svn_lkgr=
 
 while [ $# -gt 0 ]; do
   case "$1" in
-    --force-branch)
-      force_branch=yes
+    --checkout|--force-branch)
+      checkout_branch=yes
+      create_branch=yes
+      ;;
+    --create)
+      create_branch=yes
+      ;;
+    -n|--name)
+      branch_name=$2
+      create_branch=yes
+      shift
       ;;
     -q|--quiet)
       quiet=yes
       ;;
     -r|--revision)
       svn_lkgr="$2"
       shift
       ;;
     *)
       echo "Unknown option: $1"
+      echo "Usage:"
+      echo "  --checkout         Create a branch and check it out."
+      echo "  --create           Create a branch."
+      echo "  -n, --name <name>  Specify the name of branch to create or reset."
+      echo "                       This will force the branch using 'git branch -f '."
+      echo "  -q, --quiet        Quiet."
+      echo "  -r, --revision <r> Svn revision number use instead of server provided lkgr."
+      exit 1
       ;;
   esac
   shift
 done
 
 if [ -z "$svn_lkgr" ]; then
   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
@@ skipping 14 matching lines @@
 
 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.
+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
   closest_commit=
   closest_svn_commit=
 else
   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
 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 $digit + 1`
+# Determine lkgr_branch:
+if [ "${branch_name}" != "" ]; then
+  # Use the provided name for the branch.
+  lkgr_branch="${branch_name}"
+
+  # If the branch already exists, force the update to it.
+  git rev-parse --verify -q "${branch_name}" >/dev/null
+  if [ $? -eq 0 ]; then
+    old_branch_value=`git rev-parse "${branch_name}"`
+    echo "Will update branch ${lkgr_branch}, it previously was at ${old_branch_value}."
+    force_branch="--force"
+  fi
+else
+  # Pick a name for the new branch.  Use `git rev-parse` to make sure the branch
+  # doesn't already exist; if it does, iterate an integer suffix to uniquify it.
+  lkgr_branch="lkgr_r${svn_lkgr}"
+  digit=1
   git rev-parse --verify -q "${lkgr_branch}" >/dev/null
-done
+  while [ $? -eq 0 ]; do
+    lkgr_branch="lkgr_r${svn_lkgr}_${digit}"
+    digit=`expr $digit + 1`
+    git rev-parse --verify -q "${lkgr_branch}" >/dev/null
+  done
+fi
 
 if [ "${closest_svn_commit}" = "${git_lkgr}" ]; then
   echo "${closest_commit}"
-  if [ "$force_branch" = "yes" ]; then
-    git checkout -b "${lkgr_branch}" "${closest_commit}"
+  if [ "$create_branch" = "yes" ]; then
+    echo "Creating branch ${lkgr_branch}"
+    git branch ${force_branch} "${lkgr_branch}" "${closest_commit}" || exit 1
+  fi
+  if [ "$checkout_branch" = "yes" ]; then
+    git checkout "${lkgr_branch}"
   fi
   exit 0
 elif [ "${quiet}" = "yes" ]; then
   exit 1
-elif [ "${force_branch}" = "no" ]; then
+elif [ "${checkout_branch}" = "no" ]; then
   echo "There is no master commit which corresponds exactly to svn revision ${svn_lkgr}."
   if [ -n "$closest_commit" ]; then
     echo "The closest commit is ${closest_commit}."
   fi
-  read -n 1 -p "Would you like to create a new branch based on r${svn_lkgr}? (y/N) "
-  echo
-  if [ "x$REPLY" != "xy" -a "x$REPLY" != "xY" ]; then
-    exit 0
-  fi
+  echo "Call 'git lkgr --checkout' to create a branch with a commit to match ${svn_lkgr}."
+  exit 0
 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
+git branch ${force_branch} "${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
 
+git checkout "${lkgr_branch}"
+
 cat <<EOF
 
 --------------------------------------------------------------------------------
 The new branch "$lkgr_branch" was branched from this commit:
 
 $git_lkgr
 
 ... which maps to the svn 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