Add change HEAD cli option to gerrit_client

This option modifies default branch of desired repository.

R=ehmaldonaldo@chromium.org, gavinmak@google.com

Change-Id: I1e20dc8d333c4301eacffff5049e3a98c3d59f75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2575884
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
diff --git a/gerrit_client.py b/gerrit_client.py
index 1a333a5..6a174b3 100755
--- a/gerrit_client.py
+++ b/gerrit_client.py
@@ -98,6 +98,35 @@
 
 
 @subcommand.usage('[args ...]')
+def CMDhead(parser, args):
+  parser.add_option('--branch', dest='branch', help='branch name')
+
+  (opt, args) = parser.parse_args(args)
+  assert opt.project, "--project not defined"
+  assert opt.branch, "--branch not defined"
+
+  project = quote_plus(opt.project)
+  host = urlparse.urlparse(opt.host).netloc
+  branch = quote_plus(opt.branch)
+  result = gerrit_util.UpdateHead(host, project, branch)
+  logging.info(result)
+  write_result(result, opt)
+
+
+@subcommand.usage('[args ...]')
+def CMDheadinfo(parser, args):
+
+  (opt, args) = parser.parse_args(args)
+  assert opt.project, "--project not defined"
+
+  project = quote_plus(opt.project)
+  host = urlparse.urlparse(opt.host).netloc
+  result = gerrit_util.GetHead(host, project)
+  logging.info(result)
+  write_result(result, opt)
+
+
+@subcommand.usage('[args ...]')
 def CMDchanges(parser, args):
   parser.add_option('-p', '--param', dest='params', action='append',
                     help='repeatable query parameter, format: -p key=value')