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>

Documentation/rev-list-options.txt

@@ -619,9 +619,14 @@ These options are mostly targeted for packing of git repositories.
 	Only useful with '--objects'; print the object IDs that are not
 	in packs.
 
---no-walk::
+--no-walk[=(sorted|unsorted)]::
 
-	Only show the given revs, but do not traverse their ancestors.
+	Only show the given commits, but do not traverse their ancestors.
+	This has no effect if a range is specified. If the argument
+	"unsorted" is given, the commits are show in the order they were
+	given on the command line. Otherwise (if "sorted" or no argument
+	was given), the commits are show in reverse chronological order
+	by commit time.
 
 --do-walk::
 

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));

builtin/revert.c

@@ -193,7 +193,7 @@ static void parse_args(int argc, const char **argv, struct replay_opts *opts)
 		struct setup_revision_opt s_r_opt;
 		opts->revs = xmalloc(sizeof(*opts->revs));
 		init_revisions(opts->revs, NULL);
-		opts->revs->no_walk = 1;
+		opts->revs->no_walk = REVISION_WALK_NO_WALK_SORTED;
 		if (argc < 2)
 			usage_with_options(usage_str, options);
 		memset(&s_r_opt, 0, sizeof(s_r_opt));

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)

revision.h

@@ -41,6 +41,10 @@ struct rev_cmdline_info {
 	} *rev;
 };
 
+#define REVISION_WALK_WALK 0
+#define REVISION_WALK_NO_WALK_SORTED 1
+#define REVISION_WALK_NO_WALK_UNSORTED 2
+
 struct rev_info {
 	/* Starting list */
 	struct commit_list *commits;
@@ -62,7 +66,7 @@ struct rev_info {
 	/* Traversal flags */
 	unsigned int	dense:1,
 			prune:1,
-			no_walk:1,
+			no_walk:2,
 			show_all:1,
 			remove_empty_trees:1,
 			simplify_history:1,

t/t4202-log.sh

@@ -178,11 +178,21 @@ test_expect_success 'git log --no-walk <commits> sorts by commit time' '
 	test_cmp expect actual
 '
 
+test_expect_success 'git log --no-walk=sorted <commits> sorts by commit time' '
+	git log --no-walk=sorted --oneline 5d31159 804a787 394ef78 > actual &&
+	test_cmp expect actual
+'
+
 cat > expect << EOF
 5d31159 fourth
 804a787 sixth
 394ef78 fifth
 EOF
+test_expect_success 'git log --no-walk=unsorted <commits> leaves list of commits as given' '
+	git log --no-walk=unsorted --oneline 5d31159 804a787 394ef78 > actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'git show <commits> leaves list of commits as given' '
 	git show --oneline -s 5d31159 804a787 394ef78 > actual &&
 	test_cmp expect actual