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Re: [PATCH v2 1/1] pack-objects: ignore ambiguous object warnings

Jeff King <peff@xxxxxxxx> writes:

> So we'd never expect to see anything except "1" in our save_warning
> variable. Doing a save/restore is just about code hygiene and
> maintainability.

Here is what I plan to queue.  Thanks, both.

-- >8 --
From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
Date: Tue, 6 Nov 2018 12:34:47 -0800
Subject: [PATCH] pack-objects: ignore ambiguous object warnings

A git push process runs several processes during its run, but one
includes git send-pack which calls git pack-objects and passes
the known have/wants into stdin using object ids. However, the
default setting for core.warnAmbiguousRefs requires git pack-objects
to check for ref names matching the ref_rev_parse_rules array in
refs.c. This means that every object is triggering at least six
"file exists?" queries.  When there are a lot of refs, this can
add up significantly! I observed a simple push spending three
seconds checking these paths.

The fix here is similar to 4c30d50 "rev-list: disable object/refname
ambiguity check with --stdin".  While the get_object_list() method
reads the objects from stdin, turn warn_on_object_refname_ambiguity
flag (which is usually true) to false.  Just for code hygiene, save
away the original at the beginning and restore it once we are done.

Helped-by: Jeff King <peff@xxxxxxxx>
Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
 builtin/pack-objects.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index d1144a8f7e..f703e6df9b 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -2988,6 +2988,7 @@ static void get_object_list(int ac, const char **av)
 	struct rev_info revs;
 	char line[1000];
 	int flags = 0;
+	int save_warning;
 	init_revisions(&revs, NULL);
 	save_commit_buffer = 0;
@@ -2996,6 +2997,9 @@ static void get_object_list(int ac, const char **av)
 	/* make sure shallows are read */
+	save_warning = warn_on_object_refname_ambiguity;
+	warn_on_object_refname_ambiguity = 0;
 	while (fgets(line, sizeof(line), stdin) != NULL) {
 		int len = strlen(line);
 		if (len && line[len - 1] == '\n')
@@ -3022,6 +3026,8 @@ static void get_object_list(int ac, const char **av)
 			die(_("bad revision '%s'"), line);
+	warn_on_object_refname_ambiguity = save_warning;
 	if (use_bitmap_index && !get_object_list_from_bitmap(&revs))