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, 7 insertions, 4 deletions

diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index fadd3ec14c..cce42ae1dd 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -16,6 +16,7 @@
 #include "reflog-walk.h"
 #include "oidset.h"
 #include "packfile.h"
+#include "object-store.h"
 
 static const char rev_list_usage[] =
 "git rev-list [OPTION] <commit-id>... [ -- paths... ]\n"
@@ -514,8 +515,9 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 		if (revs.count && !revs.left_right && !revs.cherry_mark) {
 			uint32_t commit_count;
 			int max_count = revs.max_count;
-			if (!prepare_bitmap_walk(&revs)) {
-				count_bitmap_commit_list(&commit_count, NULL, NULL, NULL);
+			struct bitmap_index *bitmap_git;
+			if ((bitmap_git = prepare_bitmap_walk(&revs))) {
+				count_bitmap_commit_list(bitmap_git, &commit_count, NULL, NULL, NULL);
 				if (max_count >= 0 && max_count < commit_count)
 					commit_count = max_count;
 				printf("%d\n", commit_count);
@@ -523,8 +525,9 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 			}
 		} else if (revs.max_count < 0 &&
 			   revs.tag_objects && revs.tree_objects && revs.blob_objects) {
-			if (!prepare_bitmap_walk(&revs)) {
-				traverse_bitmap_commit_list(&show_object_fast);
+			struct bitmap_index *bitmap_git;
+			if ((bitmap_git = prepare_bitmap_walk(&revs))) {
+				traverse_bitmap_commit_list(bitmap_git, &show_object_fast);
 				return 0;
 			}
 		}