dag: pass unknown arguments along to git-log

Use parse_known_args() and arrange for all unknown arguments to be
passed along to git-log via the dag query.  This allows any git-log
specific option to be passed to git-dag without its command-line parser
getting in the way.

Closes #389

Signed-off-by: David Aguilar <davvid@gmail.com>

bin/git-dag

@@ -73,7 +73,12 @@ def parse_args():
                         help='number of commits to display')
     parser.add_argument('args', nargs='*', metavar='<args>',
                         help='git log arguments')
-    return parser.parse_args()
+    args, rest = parser.parse_known_args()
+    if rest:
+        # splice unknown arguments to the beginning ~
+        # these are forwarded to git-log(1).
+        args.args[:0] = rest
+    return args
 
 
 def cmd_dag(args):

share/doc/git-cola/relnotes.rst

@@ -2,6 +2,10 @@ git-cola v2.1.0
 ===============
 Usability, bells and whistles
 -----------------------------
+* `git dag` now forwards all unknown arguments along to `git log`.
+
+  https://github.com/git-cola/git-cola/issues/389
+
 * Line-by-line interactive staging was made more precise.
 
 git-cola v2.0.8