Add git-map and git-short-map to depot_tools.

git_number.py

Index: git_number.py
diff --git a/git_number.py b/git_number.py
index 04f676c655d8db6c75c36a6205e1ef152365e8e3..6c11cee23433332d2ddd748570efa6d2bec8badc 100755
--- a/git_number.py
+++ b/git_number.py
@@ -153,7 +153,7 @@ def finalize(targets):
     assert updater.returncode == 0
 
     tree_id = git.run('write-tree', env=env)
-    commit_cmd = ['commit-tree', '-m', msg, '-p'] + git.hashes(REF)
+    commit_cmd = ['commit-tree', '-m', msg, '-p'] + git.hash_multi(REF)
     for t in targets:
       commit_cmd.extend(['-p', binascii.hexlify(t)])
     commit_cmd.append(tree_id)