builtin/pack-objects.c: support --max-pack-size with --cruft

When pack-objects learned the `--cruft` option back in b757353676
(builtin/pack-objects.c: --cruft without expiration, 2022-05-20), we
explicitly forbade `--cruft` with `--max-pack-size`.

At the time, there was no specific rationale given in the patch for not
supporting the `--max-pack-size` option with `--cruft`. (As best I can
remember, it's because we were trying to push users towards only ever
having a single cruft pack, but I cannot be sure).

However, `--max-pack-size` is flexible enough that it already works with
`--cruft` and can shard unreachable objects across multiple cruft packs,
creating separate ".mtimes" files as appropriate. In fact, the
`--max-pack-size` option worked with `--cruft` as far back as
b757353676!

This is because we overwrite the `written_list`, and pass down the
appropriate length, i.e. the number of objects written in each pack
shard.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-pack-objects.txt

@@ -116,9 +116,7 @@ unreachable object whose mtime is newer than the `--cruft-expiration`).
 +
 Incompatible with `--unpack-unreachable`, `--keep-unreachable`,
 `--pack-loose-unreachable`, `--stdin-packs`, as well as any other
-options which imply `--revs`. Also incompatible with `--max-pack-size`;
-when this option is set, the maximum pack size is not inferred from
-`pack.packSizeLimit`.
+options which imply `--revs`.
 
 --cruft-expiration=<approxidate>::
 	If specified, objects are eliminated from the cruft pack if they

builtin/pack-objects.c

@@ -4382,7 +4382,7 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 
 	if (!HAVE_THREADS && delta_search_threads != 1)
 		warning(_("no threads support, ignoring --threads"));
-	if (!pack_to_stdout && !pack_size_limit && !cruft)
+	if (!pack_to_stdout && !pack_size_limit)
 		pack_size_limit = pack_size_limit_cfg;
 	if (pack_to_stdout && pack_size_limit)
 		die(_("--max-pack-size cannot be used to build a pack for transfer"));
@@ -4414,8 +4414,6 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 			die(_("cannot use internal rev list with --cruft"));
 		if (stdin_packs)
 			die(_("cannot use --stdin-packs with --cruft"));
-		if (pack_size_limit)
-			die(_("cannot use --max-pack-size with --cruft"));
 	}
 
 	/*

builtin/repack.c

@@ -720,7 +720,6 @@ static int write_cruft_pack(const struct pack_objects_args *args,
 
 	strvec_push(&cmd.args, "--honor-pack-keep");
 	strvec_push(&cmd.args, "--non-empty");
-	strvec_push(&cmd.args, "--max-pack-size=0");
 
 	cmd.in = -1;
 
@@ -1048,6 +1047,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 			cruft_po_args.depth = po_args.depth;
 		if (!cruft_po_args.threads)
 			cruft_po_args.threads = po_args.threads;
+		if (!cruft_po_args.max_pack_size)
+			cruft_po_args.max_pack_size = po_args.max_pack_size;
 
 		cruft_po_args.local = po_args.local;
 		cruft_po_args.quiet = po_args.quiet;

t/t5329-pack-objects-cruft.sh

@@ -573,23 +573,54 @@ test_expect_success 'cruft repack with no reachable objects' '
 	)
 '
 
-test_expect_success 'cruft repack ignores --max-pack-size' '
+write_blob () {
+	test-tool genrandom "$@" >in &&
+	git hash-object -w -t blob in
+}
+
+find_pack () {
+	for idx in $(ls $packdir/pack-*.idx)
+	do
+		git show-index <$idx >out &&
+		if grep -q "$1" out
+		then
+			echo $idx
+		fi || return 1
+	done
+}
+
+test_expect_success 'cruft repack with --max-pack-size' '
 	git init max-pack-size &&
 	(
 		cd max-pack-size &&
 		test_commit base &&
+
 		# two cruft objects which exceed the maximum pack size
-		test-tool genrandom foo 1048576 | git hash-object --stdin -w &&
-		test-tool genrandom bar 1048576 | git hash-object --stdin -w &&
+		foo=$(write_blob foo 1048576) &&
+		bar=$(write_blob bar 1048576) &&
+		test-tool chmtime --get -1000 \
+			"$objdir/$(test_oid_to_path $foo)" >foo.mtime &&
+		test-tool chmtime --get -2000 \
+			"$objdir/$(test_oid_to_path $bar)" >bar.mtime &&
 		git repack --cruft --max-pack-size=1M &&
 		find $packdir -name "*.mtimes" >cruft &&
-		test_line_count = 1 cruft &&
-		test-tool pack-mtimes "$(basename "$(cat cruft)")" >objects &&
-		test_line_count = 2 objects
+		test_line_count = 2 cruft &&
+
+		foo_mtimes="$(basename $(find_pack $foo) .idx).mtimes" &&
+		bar_mtimes="$(basename $(find_pack $bar) .idx).mtimes" &&
+		test-tool pack-mtimes $foo_mtimes >foo.actual &&
+		test-tool pack-mtimes $bar_mtimes >bar.actual &&
+
+		echo "$foo $(cat foo.mtime)" >foo.expect &&
+		echo "$bar $(cat bar.mtime)" >bar.expect &&
+
+		test_cmp foo.expect foo.actual &&
+		test_cmp bar.expect bar.actual &&
+		test "$foo_mtimes" != "$bar_mtimes"
 	)
 '
 
-test_expect_success 'cruft repack ignores pack.packSizeLimit' '
+test_expect_success 'cruft repack with pack.packSizeLimit' '
 	(
 		cd max-pack-size &&
 		# repack everything back together to remove the existing cruft
@@ -599,9 +630,12 @@ test_expect_success 'cruft repack ignores pack.packSizeLimit' '
 		# ensure the same post condition is met when --max-pack-size
 		# would otherwise be inferred from the configuration
 		find $packdir -name "*.mtimes" >cruft &&
-		test_line_count = 1 cruft &&
-		test-tool pack-mtimes "$(basename "$(cat cruft)")" >objects &&
-		test_line_count = 2 objects
+		test_line_count = 2 cruft &&
+		for pack in $(cat cruft)
+		do
+			test-tool pack-mtimes "$(basename $pack)" >objects &&
+			test_line_count = 1 objects || return 1
+		done
 	)
 '