add --help option

This only affects invocation of git-deps directly, not via the git(1)
wrapper, since the latter will still issue the error:

    No manual entry for git-deps

Signed-off-by: Adam Spiers <git@adamspiers.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/git-deps b/git-deps
index b814e88..ed02be0 100755
--- a/git-deps
+++ b/git-deps
@@ -609,7 +609,7 @@ def parse_args():
         usage='%(prog)s [options] COMMIT-ISH [COMMIT-ISH...]',
         add_help=False
     )
-    parser.add_argument('-h', action='help',
+    parser.add_argument('-h', '--help', action='help',
                         help='Show this help message and exit')
     parser.add_argument('-l', '--log', dest='log', action='store_true',
                         help='Show commit logs for calculated dependencies')