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>

1 files changed, 15 insertions, 3 deletions

diff --git a/revision.c b/revision.c
index 935e7a7..2f9dbdd 100644
--- a/revision.c
+++ b/revision.c
@@ -1294,7 +1294,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	    !strcmp(arg, "--no-walk") || !strcmp(arg, "--do-walk") ||
 	    !strcmp(arg, "--bisect") || !prefixcmp(arg, "--glob=") ||
 	    !prefixcmp(arg, "--branches=") || !prefixcmp(arg, "--tags=") ||
-	    !prefixcmp(arg, "--remotes="))
+	    !prefixcmp(arg, "--remotes=") || !prefixcmp(arg, "--no-walk="))
 	{
 		unkv[(*unkc)++] = arg;
 		return 1;
@@ -1687,7 +1687,18 @@ static int handle_revision_pseudo_opt(const char *submodule,
 	} else if (!strcmp(arg, "--not")) {
 		*flags ^= UNINTERESTING;
 	} else if (!strcmp(arg, "--no-walk")) {
-		revs->no_walk = 1;
+		revs->no_walk = REVISION_WALK_NO_WALK_SORTED;
+	} else if (!prefixcmp(arg, "--no-walk=")) {
+		/*
+		 * Detached form ("--no-walk X" as opposed to "--no-walk=X")
+		 * not allowed, since the argument is optional.
+		 */
+		if (!strcmp(arg + 10, "sorted"))
+			revs->no_walk = REVISION_WALK_NO_WALK_SORTED;
+		else if (!strcmp(arg + 10, "unsorted"))
+			revs->no_walk = REVISION_WALK_NO_WALK_UNSORTED;
+		else
+			return error("invalid argument to --no-walk");
 	} else if (!strcmp(arg, "--do-walk")) {
 		revs->no_walk = 0;
 	} else {
@@ -2091,10 +2102,11 @@ int prepare_revision_walk(struct rev_info *revs)
 		}
 		e++;
 	}
-	commit_list_sort_by_date(&revs->commits);
 	if (!revs->leak_pending)
 		free(list);
 
+	if (revs->no_walk != REVISION_WALK_NO_WALK_UNSORTED)
+		commit_list_sort_by_date(&revs->commits);
 	if (revs->no_walk)
 		return 0;
 	if (revs->limited)