pack-objects: introduce pack.allowPackReuse

peff · gitster · commit e704fc7978f2 · 2020-01-23T10:51:50.000-08:00
Let's make it possible to configure if we want pack reuse or not.

The main reason it might not be wanted is probably debugging and
performance testing, though pack reuse _might_ cause larger packs,
because we wouldn't consider the reused objects as bases for
finding new deltas.

Signed-off-by: Jeff King &lt;peff@peff.net&gt;
Signed-off-by: Christian Couder &lt;chriscool@tuxfamily.org&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/Documentation/config/pack.txt b/Documentation/config/pack.txt
@@ -27,6 +27,13 @@ Note that changing the compression level will not automatically recompress
 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,
+	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
+	true.
+
 pack.island::
 	An extended regular expression configuring a set of delta
 	islands. See "DELTA ISLANDS" in linkgit:git-pack-objects[1]
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
@@ -96,6 +96,7 @@ static off_t reuse_packfile_offset;
 
 static int use_bitmap_index_default = 1;
 static int use_bitmap_index = -1;
+static int allow_pack_reuse = 1;
 static enum {
 	WRITE_BITMAP_FALSE = 0,
 	WRITE_BITMAP_QUIET,
@@ -2715,6 +2716,10 @@ static int git_pack_config(const char *k, const char *v, void *cb)
 		use_bitmap_index_default = git_config_bool(k, v);
 		return 0;
 	}
+	if (!strcmp(k, "pack.allowpackreuse")) {
+		allow_pack_reuse = git_config_bool(k, v);
+		return 0;
+	}
 	if (!strcmp(k, "pack.usesparse")) {
 		sparse = git_config_bool(k, v);
 		return 0;
@@ -3050,7 +3055,8 @@ static void loosen_unused_packed_objects(void)
  */
 static int pack_options_allow_reuse(void)
 {
-	return pack_to_stdout &&
+	return allow_pack_reuse &&
+	       pack_to_stdout &&
 	       allow_ofs_delta &&
 	       !ignore_packed_keep_on_disk &&
 	       !ignore_packed_keep_in_core &&
