Merge branch 'tb/reverse-midx'

An on-disk reverse-index to map the in-pack location of an object
back to its object name across multiple packfiles is introduced.

* tb/reverse-midx:
  midx.c: improve cache locality in midx_pack_order_cmp()
  pack-revindex: write multi-pack reverse indexes
  pack-write.c: extract 'write_rev_file_order'
  pack-revindex: read multi-pack reverse indexes
  Documentation/technical: describe multi-pack reverse indexes
  midx: make some functions non-static
  midx: keep track of the checksum
  midx: don't free midx_name early
  midx: allow marking a pack as preferred
  t/helper/test-read-midx.c: add '--show-objects'
  builtin/multi-pack-index.c: display usage on unrecognized command
  builtin/multi-pack-index.c: don't enter bogus cmd_mode
  builtin/multi-pack-index.c: split sub-commands
  builtin/multi-pack-index.c: define common usage with a macro
  builtin/multi-pack-index.c: don't handle 'progress' separately
  builtin/multi-pack-index.c: inline 'flags' with options

1 files changed, 25 insertions, 11 deletions

diff --git a/pack-write.c b/pack-write.c
index 2ca85a9..f1fc3ec 100644
--- a/pack-write.c
+++ b/pack-write.c
@@ -201,21 +201,12 @@ static void write_rev_header(struct hashfile *f)
 }
 
 static void write_rev_index_positions(struct hashfile *f,
-				      struct pack_idx_entry **objects,
+				      uint32_t *pack_order,
 				      uint32_t nr_objects)
 {
-	uint32_t *pack_order;
 	uint32_t i;
-
-	ALLOC_ARRAY(pack_order, nr_objects);
-	for (i = 0; i < nr_objects; i++)
-		pack_order[i] = i;
-	QSORT_S(pack_order, nr_objects, pack_order_cmp, objects);
-
 	for (i = 0; i < nr_objects; i++)
 		hashwrite_be32(f, pack_order[i]);
-
-	free(pack_order);
 }
 
 static void write_rev_trailer(struct hashfile *f, const unsigned char *hash)
@@ -229,6 +220,29 @@ const char *write_rev_file(const char *rev_name,
 			   const unsigned char *hash,
 			   unsigned flags)
 {
+	uint32_t *pack_order;
+	uint32_t i;
+	const char *ret;
+
+	ALLOC_ARRAY(pack_order, nr_objects);
+	for (i = 0; i < nr_objects; i++)
+		pack_order[i] = i;
+	QSORT_S(pack_order, nr_objects, pack_order_cmp, objects);
+
+	ret = write_rev_file_order(rev_name, pack_order, nr_objects, hash,
+				   flags);
+
+	free(pack_order);
+
+	return ret;
+}
+
+const char *write_rev_file_order(const char *rev_name,
+				 uint32_t *pack_order,
+				 uint32_t nr_objects,
+				 const unsigned char *hash,
+				 unsigned flags)
+{
 	struct hashfile *f;
 	int fd;
 
@@ -262,7 +276,7 @@ const char *write_rev_file(const char *rev_name,
 
 	write_rev_header(f);
 
-	write_rev_index_positions(f, objects, nr_objects);
+	write_rev_index_positions(f, pack_order, nr_objects);
 	write_rev_trailer(f, hash);
 
 	if (rev_name && adjust_shared_perm(rev_name) < 0)