pack-bitmap: drop "loaded" flag

In the early days of the bitmap code, there was a single
static bitmap_index struct that was used behind the scenes,
and any bitmap-related functions could lazily check
bitmap_git.loaded to see if they needed to read the on-disk
data.

But since 3ae5fa0768 (pack-bitmap: remove bitmap_git global
variable, 2018-06-07), the caller is responsible for the
lifetime of the bitmap_index struct, and we return it from
prepare_bitmap_git() and prepare_bitmap_walk(), both of
which load the on-disk data (or return NULL).

So outside of these functions, it's not possible to have a
bitmap_index for which the loaded flag is not true. Nor is
it possible to accidentally pass an already-loaded
bitmap_index to the loading function (which is static-local
to the file).

We can drop this unnecessary and confusing flag.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pack-bitmap.c

@@ -91,8 +91,6 @@ struct bitmap_index {
 
 	/* Version of the bitmap index */
 	unsigned int version;
-
-	unsigned loaded : 1;
 };
 
 static struct ewah_bitmap *lookup_stored_bitmap(struct stored_bitmap *st)
@@ -306,7 +304,7 @@ static int open_pack_bitmap_1(struct bitmap_index *bitmap_git, struct packed_git
 
 static int load_pack_bitmap(struct bitmap_index *bitmap_git)
 {
-	assert(bitmap_git->map && !bitmap_git->loaded);
+	assert(bitmap_git->map);
 
 	bitmap_git->bitmaps = kh_init_sha1();
 	bitmap_git->ext_index.positions = kh_init_sha1_pos();
@@ -321,7 +319,6 @@ static int load_pack_bitmap(struct bitmap_index *bitmap_git)
 	if (load_bitmap_entries_v1(bitmap_git) < 0)
 		goto failed;
 
-	bitmap_git->loaded = 1;
 	return 0;
 
 failed:
@@ -336,7 +333,7 @@ static int open_pack_bitmap(struct bitmap_index *bitmap_git)
 	struct packed_git *p;
 	int ret = -1;
 
-	assert(!bitmap_git->map && !bitmap_git->loaded);
+	assert(!bitmap_git->map);
 
 	for (p = get_packed_git(the_repository); p; p = p->next) {
 		if (open_pack_bitmap_1(bitmap_git, p) == 0)
@@ -738,7 +735,7 @@ struct bitmap_index *prepare_bitmap_walk(struct rev_info *revs)
 	 * from disk. this is the point of no return; after this the rev_list
 	 * becomes invalidated and we must perform the revwalk through bitmaps
 	 */
-	if (!bitmap_git->loaded && load_pack_bitmap(bitmap_git) < 0)
+	if (load_pack_bitmap(bitmap_git) < 0)
 		goto cleanup;
 
 	object_array_clear(&revs->pending);