[PATCH v2 2/8] builtin/repack.c: extract marking packs for deletion

[Taylor Blau <me@ttaylorr.com>]

At the end of a repack (when given `-d`), Git attempts to remove any
packs which have been made "redundant" as a result of the repacking
operation. For example, an all-into-one (`-A` or `-a`) repack makes
every pre-existing pack which is not marked as kept redundant. Geometric
repacks (with `--geometric=<n>`) make any packs which were rolled up
redundant, and so on.

But before deleting the set of packs we think are redundant, we first
check to see whether or not we just wrote a pack which is identical to
any one of the packs we were going to delete. When this is the case, Git
must avoid deleting that pack, since it matches a pack we just wrote
(so deleting it may cause the repository to become corrupt).

Right now we only process the list of non-kept packs in a single pass.
But a future change will split the existing non-kept packs further into
two lists: one for cruft packs, and another for non-cruft packs.

Factor out this routine to prepare for calling it twice on two separate
lists in a future patch.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 builtin/repack.c | 50 +++++++++++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 18 deletions(-)

diff --git a/builtin/repack.c b/builtin/repack.c
index 67bf86567f..0eee430951 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -105,6 +105,36 @@ struct existing_packs {
 	.non_kept_packs = STRING_LIST_INIT_DUP, \
 }
 
+static void mark_packs_for_deletion_1(struct string_list *names,
+				      struct string_list *list)
+{
+	struct string_list_item *item;
+	const int hexsz = the_hash_algo->hexsz;
+
+	for_each_string_list_item(item, list) {
+		char *sha1;
+		size_t len = strlen(item->string);
+		if (len < hexsz)
+			continue;
+		sha1 = item->string + len - hexsz;
+		/*
+		 * Mark this pack for deletion, which ensures that this
+		 * pack won't be included in a MIDX (if `--write-midx`
+		 * was given) and that we will actually delete this pack
+		 * (if `-d` was given).
+		 */
+		if (!string_list_has_string(names, sha1))
+			item->util = (void*)(uintptr_t)((size_t)item->util | DELETE_PACK);
+	}
+}
+
+static void mark_packs_for_deletion(struct existing_packs *existing,
+				    struct string_list *names)
+
+{
+	mark_packs_for_deletion_1(names, &existing->non_kept_packs);
+}
+
 static void existing_packs_release(struct existing_packs *existing)
 {
 	string_list_clear(&existing->kept_packs, 0);
@@ -1142,24 +1172,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	}
 	/* End of pack replacement. */
 
-	if (delete_redundant && pack_everything & ALL_INTO_ONE) {
-		const int hexsz = the_hash_algo->hexsz;
-		for_each_string_list_item(item, &existing.non_kept_packs) {
-			char *sha1;
-			size_t len = strlen(item->string);
-			if (len < hexsz)
-				continue;
-			sha1 = item->string + len - hexsz;
-			/*
-			 * Mark this pack for deletion, which ensures that this
-			 * pack won't be included in a MIDX (if `--write-midx`
-			 * was given) and that we will actually delete this pack
-			 * (if `-d` was given).
-			 */
-			if (!string_list_has_string(&names, sha1))
-				item->util = (void*)(uintptr_t)((size_t)item->util | DELETE_PACK);
-		}
-	}
+	if (delete_redundant && pack_everything & ALL_INTO_ONE)
+		mark_packs_for_deletion(&existing, &names);
 
 	if (write_midx) {
 		struct string_list include = STRING_LIST_INIT_NODUP;
-- 
2.42.0.166.g68748eb9c8