path: root/builtin/multi-pack-index.c
diff options
authorTaylor Blau <>2021-03-30 15:04:11 (GMT)
committerJunio C Hamano <>2021-04-01 20:07:37 (GMT)
commit9218c6a40c37023a1f434222d501218cf8157857 (patch)
tree04e21a6dcb3a8f1e11c151597a5fcf31be20f44d /builtin/multi-pack-index.c
parent86d174b7246b634ddb991d67e1ee4575fcc8d1e4 (diff)
midx: allow marking a pack as preferred
When multiple packs in the multi-pack index contain the same object, the MIDX machinery must make a choice about which pack it associates with that object. Prior to this patch, the lowest-ordered[1] pack was always selected. Pack selection for duplicate objects is relatively unimportant today, but it will become important for multi-pack bitmaps. This is because we can only invoke the pack-reuse mechanism when all of the bits for reused objects come from the reuse pack (in order to ensure that all reused deltas can find their base objects in the same pack). To encourage the pack selection process to prefer one pack over another (the pack to be preferred is the one a caller would like to later use as a reuse pack), introduce the concept of a "preferred pack". When provided, the MIDX code will always prefer an object found in a preferred pack over any other. No format changes are required to store the preferred pack, since it will be able to be inferred with a corresponding MIDX bitmap, by looking up the pack associated with the object in the first bit position (this ordering is described in detail in a subsequent commit). [1]: the ordering is specified by MIDX internals; for our purposes we can consider the "lowest ordered" pack to be "the one with the most-recent mtime. Signed-off-by: Taylor Blau <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 'builtin/multi-pack-index.c')
1 files changed, 16 insertions, 3 deletions
diff --git a/builtin/multi-pack-index.c b/builtin/multi-pack-index.c
index 8711174..5d3ea44 100644
--- a/builtin/multi-pack-index.c
+++ b/builtin/multi-pack-index.c
@@ -4,9 +4,10 @@
#include "parse-options.h"
#include "midx.h"
#include "trace2.h"
+#include "object-store.h"
- N_("git multi-pack-index [<options>] write")
+ N_("git multi-pack-index [<options>] write [--preferred-pack=<pack>]")
N_("git multi-pack-index [<options>] verify")
@@ -43,6 +44,7 @@ static char const * const builtin_multi_pack_index_usage[] = {
static struct opts_multi_pack_index {
const char *object_dir;
+ const char *preferred_pack;
unsigned long batch_size;
unsigned flags;
} opts;
@@ -61,7 +63,15 @@ static struct option *add_common_options(struct option *prev)
static int cmd_multi_pack_index_write(int argc, const char **argv)
- struct option *options = common_opts;
+ struct option *options;
+ static struct option builtin_multi_pack_index_write_options[] = {
+ OPT_STRING(0, "preferred-pack", &opts.preferred_pack,
+ N_("preferred-pack"),
+ N_("pack for reuse when computing a multi-pack bitmap")),
+ OPT_END(),
+ };
+ options = add_common_options(builtin_multi_pack_index_write_options);
@@ -72,7 +82,10 @@ static int cmd_multi_pack_index_write(int argc, const char **argv)
- return write_midx_file(opts.object_dir, opts.flags);
+ FREE_AND_NULL(options);
+ return write_midx_file(opts.object_dir, opts.preferred_pack,
+ opts.flags);
static int cmd_multi_pack_index_verify(int argc, const char **argv)