Merge branch 'tb/multi-cruft-pack'

Use of --max-pack-size to allow multiple packfiles to be created is
now supported even when we are sending unreachable objects to cruft
packs.

* tb/multi-cruft-pack:
  Documentation/gitformat-pack.txt: drop mixed version section
  Documentation/gitformat-pack.txt: remove multi-cruft packs alternative
  builtin/pack-objects.c: support `--max-pack-size` with `--cruft`
  builtin/pack-objects.c: remove unnecessary strbuf_reset()

Author: gitster

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

Documentation/gitformat-pack.txt

@@ -588,51 +588,17 @@ later on.
 It is linkgit:git-gc[1] that is typically responsible for removing expired
 unreachable objects.
 
-=== Caution for mixed-version environments
-
-Repositories that have cruft packs in them will continue to work with any older
-version of Git. Note, however, that previous versions of Git which do not
-understand the `.mtimes` file will use the cruft pack's mtime as the mtime for
-all of the objects in it. In other words, do not expect older (pre-cruft pack)
-versions of Git to interpret or even read the contents of the `.mtimes` file.
-
-Note that having mixed versions of Git GC-ing the same repository can lead to
-unreachable objects never being completely pruned. This can happen under the
-following circumstances:
-
-  - An older version of Git running GC explodes the contents of an existing
-    cruft pack loose, using the cruft pack's mtime.
-  - A newer version running GC collects those loose objects into a cruft pack,
-    where the .mtime file reflects the loose object's actual mtimes, but the
-    cruft pack mtime is "now".
-
-Repeating this process will lead to unreachable objects not getting pruned as a
-result of repeatedly resetting the objects' mtimes to the present time.
-
-If you are GC-ing repositories in a mixed version environment, consider omitting
-the `--cruft` option when using linkgit:git-repack[1] and linkgit:git-gc[1], and
-setting the `gc.cruftPacks` configuration to "false" until all writers
-understand cruft packs.
-
 === Alternatives
 
 Notable alternatives to this design include:
 
-  - The location of the per-object mtime data, and
-  - Storing unreachable objects in multiple cruft packs.
+  - The location of the per-object mtime data.
 
 On the location of mtime data, a new auxiliary file tied to the pack was chosen
 to avoid complicating the `.idx` format. If the `.idx` format were ever to gain
 support for optional chunks of data, it may make sense to consolidate the
 `.mtimes` format into the `.idx` itself.
 
-Storing unreachable objects among multiple cruft packs (e.g., creating a new
-cruft pack during each repacking operation including only unreachable objects
-which aren't already stored in an earlier cruft pack) is significantly more
-complicated to construct, and so aren't pursued here. The obvious drawback to
-the current implementation is that the entire cruft pack must be re-written from
-scratch.
-
 GIT
 ---
 Part of the linkgit:git[1] suite

builtin/pack-objects.c

@@ -3603,7 +3603,6 @@ static void read_cruft_objects(void)
 			string_list_append(&discard_packs, buf.buf + 1);
 		else
 			string_list_append(&fresh_packs, buf.buf);
-		strbuf_reset(&buf);
 	}
 
 	string_list_sort(&discard_packs);
@@ -4383,7 +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"));
@@ -4415,8 +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
 	)
 '