pack-bitmap: remove bitmap_git global variable

Remove the bitmap_git global variable. Instead, generate on demand an
instance of struct bitmap_index for code that needs to access it.

This allows us significant control over the lifetime of instances of
struct bitmap_index. In particular, packs can now be closed without
worrying if an unnecessarily long-lived "pack" field in struct
bitmap_index still points to it.

The bitmap API is also clearer in that we need to first obtain a struct
bitmap_index, then we use it.

This patch raises two potential issues: (1) memory for the struct
bitmap_index is allocated without being freed, and (2)
prepare_bitmap_git() and prepare_bitmap_walk() can reuse a previously
loaded bitmap. For (1), this will be dealt with in a subsequent patch in
this patch set that also deals with freeing the contents of the struct
bitmap_index (which were not freed previously, because they have global
scope). For (2), current bitmap users only load the bitmap once at most
(note that pack-objects can use bitmaps or write bitmaps, but not both
at the same time), so support for reuse has no effect - and future users
can pass around the struct bitmap_index * obtained if they need to do 2
or more things with the same bitmap.

Helped-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 71056d8294..d064f944b0 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -2929,11 +2929,13 @@ static int pack_options_allow_reuse(void)
 
 static int get_object_list_from_bitmap(struct rev_info *revs)
 {
-	if (prepare_bitmap_walk(revs) < 0)
+	struct bitmap_index *bitmap_git;
+	if (!(bitmap_git = prepare_bitmap_walk(revs)))
 		return -1;
 
 	if (pack_options_allow_reuse() &&
 	    !reuse_partial_packfile_from_bitmap(
+			bitmap_git,
 			&reuse_packfile,
 			&reuse_packfile_objects,
 			&reuse_packfile_offset)) {
@@ -2942,7 +2944,7 @@ static int get_object_list_from_bitmap(struct rev_info *revs)
 		display_progress(progress_state, nr_result);
 	}
 
-	traverse_bitmap_commit_list(&add_object_entry_from_bitmap);
+	traverse_bitmap_commit_list(bitmap_git, &add_object_entry_from_bitmap);
 	return 0;
 }