Added hyphen-only options

Some options have words separated by underscores. Added options with
same name and underscores replaced by hyphens.

BUG=400953

Review URL: https://codereview.chromium.org/436963005

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@288366 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/git_new_branch.py b/git_new_branch.py
index 6c3f39f..18ce018 100755
--- a/git_new_branch.py
+++ b/git_new_branch.py
@@ -18,7 +18,8 @@
   )
   parser.add_argument('branch_name')
   g = parser.add_mutually_exclusive_group()
-  g.add_argument('--upstream_current', action='store_true',
+  g.add_argument('--upstream-current', '--upstream_current',
+                 action='store_true',
                  help='set upstream branch to current branch.')
   g.add_argument('--upstream', metavar='REF', default=root(),
                  help='upstream branch (or tag) to track.')