[PATCH v2 24/26] pack-objects: allow setting `pack.allowPackReuse` to "single"

[Taylor Blau <me@ttaylorr.com>]

In e704fc7978 (pack-objects: introduce pack.allowPackReuse, 2019-12-18),
the `pack.allowPackReuse` configuration option was introduced, allowing
users to disable the pack reuse mechanism.

To prepare for debugging multi-pack reuse, allow setting configuration
to "single" in addition to the usual bool-or-int values.

"single" implies the same behavior as "true", "1", "yes", and so on. But
it will complement a new "multi" value (to be introduced in a future
commit). When set to "single", we will only perform pack reuse on a
single pack, regardless of whether or not there are multiple MIDX'd
packs.

This requires no code changes (yet), since we only support single pack
reuse.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 Documentation/config/pack.txt |  2 +-
 builtin/pack-objects.c        | 19 ++++++++++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/Documentation/config/pack.txt b/Documentation/config/pack.txt
index f50df9dbce..fe100d0fb7 100644
--- a/Documentation/config/pack.txt
+++ b/Documentation/config/pack.txt
@@ -28,7 +28,7 @@ all existing objects. You can force recompression by passing the -F option
 to linkgit:git-repack[1].
 
 pack.allowPackReuse::
-	When true, and when reachability bitmaps are enabled,
+	When true or "single", and when reachability bitmaps are enabled,
 	pack-objects will try to send parts of the bitmapped packfile
 	verbatim. This can reduce memory and CPU usage to serve fetches,
 	but might result in sending a slightly larger pack. Defaults to
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 7aae9f104b..684698f679 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -229,7 +229,10 @@ static struct bitmap *reuse_packfile_bitmap;
 
 static int use_bitmap_index_default = 1;
 static int use_bitmap_index = -1;
-static int allow_pack_reuse = 1;
+static enum {
+	NO_PACK_REUSE = 0,
+	SINGLE_PACK_REUSE,
+} allow_pack_reuse = SINGLE_PACK_REUSE;
 static enum {
 	WRITE_BITMAP_FALSE = 0,
 	WRITE_BITMAP_QUIET,
@@ -3244,7 +3247,17 @@ static int git_pack_config(const char *k, const char *v,
 		return 0;
 	}
 	if (!strcmp(k, "pack.allowpackreuse")) {
-		allow_pack_reuse = git_config_bool(k, v);
+		int res = git_parse_maybe_bool_text(v);
+		if (res < 0) {
+			if (!strcasecmp(v, "single"))
+				allow_pack_reuse = SINGLE_PACK_REUSE;
+			else
+				die(_("invalid pack.allowPackReuse value: '%s'"), v);
+		} else if (res) {
+			allow_pack_reuse = SINGLE_PACK_REUSE;
+		} else {
+			allow_pack_reuse = NO_PACK_REUSE;
+		}
 		return 0;
 	}
 	if (!strcmp(k, "pack.threads")) {
@@ -3999,7 +4012,7 @@ static void loosen_unused_packed_objects(void)
  */
 static int pack_options_allow_reuse(void)
 {
-	return allow_pack_reuse &&
+	return allow_pack_reuse != NO_PACK_REUSE &&
 	       pack_to_stdout &&
 	       !ignore_packed_keep_on_disk &&
 	       !ignore_packed_keep_in_core &&
-- 
2.43.0.102.ga31d690331.dirty