teach log --no-walk=unsorted, which avoids sorting

When 'git log' is passed the --no-walk option, no revision walk takes
place, naturally. Perhaps somewhat surprisingly, however, the provided
revisions still get sorted by commit date. So e.g 'git log --no-walk
HEAD HEAD~1' and 'git log --no-walk HEAD~1 HEAD' give the same result
(unless the two revisions share the commit date, in which case they
will retain the order given on the command line). As the commit that
introduced --no-walk (8e64006 (Teach revision machinery about
--no-walk, 2007-07-24)) points out, the sorting is intentional, to
allow things like

 git log --abbrev-commit --pretty=oneline --decorate --all --no-walk

to show all refs in order by commit date.

But there are also other cases where the sorting is not wanted, such
as

 <command producing revisions in order> |
       git log --oneline --no-walk --stdin

To accomodate both cases, leave the decision of whether or not to sort
up to the caller, by allowing --no-walk={sorted,unsorted}, defaulting
to 'sorted' for backward-compatibility reasons.

Signed-off-by: Martin von Zweigbergk <martinvonz@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/log.c

@@ -454,7 +454,7 @@ int cmd_show(int argc, const char **argv, const char *prefix)
 	init_revisions(&rev, prefix);
 	rev.diff = 1;
 	rev.always_show_header = 1;
-	rev.no_walk = 1;
+	rev.no_walk = REVISION_WALK_NO_WALK_SORTED;
 	rev.diffopt.stat_width = -1; 	/* Scale to real terminal size */
 
 	memset(&opt, 0, sizeof(opt));