Merge branch 'tb/midx-write-cleanup'

Code clean-up around writing the .midx files.

* tb/midx-write-cleanup:
  pack-bitmap.c: reimplement `midx_bitmap_filename()` with helper
  midx: replace `get_midx_rev_filename()` with a generic helper
  midx-write.c: support reading an existing MIDX with `packs_to_include`
  midx-write.c: extract `fill_packs_from_midx()`
  midx-write.c: extract `should_include_pack()`
  midx-write.c: pass `start_pack` to `compute_sorted_entries()`
  midx-write.c: reduce argument count for `get_sorted_entries()`
  midx-write.c: tolerate `--preferred-pack` without bitmaps

midx-write.c

@@ -100,6 +100,18 @@ struct write_midx_context {
 	struct string_list *to_include;
 };
 
+static int should_include_pack(const struct write_midx_context *ctx,
+			       const char *file_name,
+			       int exclude_from_midx)
+{
+	if (exclude_from_midx && ctx->m && midx_contains_pack(ctx->m, file_name))
+		return 0;
+	if (ctx->to_include && !string_list_has_string(ctx->to_include,
+						       file_name))
+		return 0;
+	return 1;
+}
+
 static void add_pack_to_midx(const char *full_path, size_t full_path_len,
 			     const char *file_name, void *data)
 {
@@ -108,29 +120,11 @@ static void add_pack_to_midx(const char *full_path, size_t full_path_len,
 
 	if (ends_with(file_name, ".idx")) {
 		display_progress(ctx->progress, ++ctx->pack_paths_checked);
-		/*
-		 * Note that at most one of ctx->m and ctx->to_include are set,
-		 * so we are testing midx_contains_pack() and
-		 * string_list_has_string() independently (guarded by the
-		 * appropriate NULL checks).
-		 *
-		 * We could support passing to_include while reusing an existing
-		 * MIDX, but don't currently since the reuse process drags
-		 * forward all packs from an existing MIDX (without checking
-		 * whether or not they appear in the to_include list).
-		 *
-		 * If we added support for that, these next two conditional
-		 * should be performed independently (likely checking
-		 * to_include before the existing MIDX).
-		 */
-		if (ctx->m && midx_contains_pack(ctx->m, file_name))
-			return;
-		else if (ctx->to_include &&
-			 !string_list_has_string(ctx->to_include, file_name))
+
+		if (!should_include_pack(ctx, file_name, 1))
 			return;
 
 		ALLOC_GROW(ctx->info, ctx->nr + 1, ctx->alloc);
-
 		p = add_packed_git(full_path, full_path_len, 0);
 		if (!p) {
 			warning(_("failed to add packfile '%s'"),
@@ -299,21 +293,16 @@ static void midx_fanout_add_pack_fanout(struct midx_fanout *fanout,
  * Copy only the de-duplicated entries (selected by most-recent modified time
  * of a packfile containing the object).
  */
-static struct pack_midx_entry *get_sorted_entries(struct multi_pack_index *m,
-						  struct pack_info *info,
-						  uint32_t nr_packs,
-						  size_t *nr_objects,
-						  int preferred_pack)
+static void compute_sorted_entries(struct write_midx_context *ctx,
+				   uint32_t start_pack)
 {
 	uint32_t cur_fanout, cur_pack, cur_object;
 	size_t alloc_objects, total_objects = 0;
 	struct midx_fanout fanout = { 0 };
-	struct pack_midx_entry *deduplicated_entries = NULL;
-	uint32_t start_pack = m ? m->num_packs : 0;
 
-	for (cur_pack = start_pack; cur_pack < nr_packs; cur_pack++)
+	for (cur_pack = start_pack; cur_pack < ctx->nr; cur_pack++)
 		total_objects = st_add(total_objects,
-				       info[cur_pack].p->num_objects);
+				       ctx->info[cur_pack].p->num_objects);
 
 	/*
 	 * As we de-duplicate by fanout value, we expect the fanout
@@ -323,26 +312,26 @@ static struct pack_midx_entry *get_sorted_entries(struct multi_pack_index *m,
 	alloc_objects = fanout.alloc = total_objects > 3200 ? total_objects / 200 : 16;
 
 	ALLOC_ARRAY(fanout.entries, fanout.alloc);
-	ALLOC_ARRAY(deduplicated_entries, alloc_objects);
-	*nr_objects = 0;
+	ALLOC_ARRAY(ctx->entries, alloc_objects);
+	ctx->entries_nr = 0;
 
 	for (cur_fanout = 0; cur_fanout < 256; cur_fanout++) {
 		fanout.nr = 0;
 
-		if (m)
-			midx_fanout_add_midx_fanout(&fanout, m, cur_fanout,
-						    preferred_pack);
+		if (ctx->m)
+			midx_fanout_add_midx_fanout(&fanout, ctx->m, cur_fanout,
+						    ctx->preferred_pack_idx);
 
-		for (cur_pack = start_pack; cur_pack < nr_packs; cur_pack++) {
-			int preferred = cur_pack == preferred_pack;
+		for (cur_pack = start_pack; cur_pack < ctx->nr; cur_pack++) {
+			int preferred = cur_pack == ctx->preferred_pack_idx;
 			midx_fanout_add_pack_fanout(&fanout,
-						    info, cur_pack,
+						    ctx->info, cur_pack,
 						    preferred, cur_fanout);
 		}
 
-		if (-1 < preferred_pack && preferred_pack < start_pack)
-			midx_fanout_add_pack_fanout(&fanout, info,
-						    preferred_pack, 1,
+		if (-1 < ctx->preferred_pack_idx && ctx->preferred_pack_idx < start_pack)
+			midx_fanout_add_pack_fanout(&fanout, ctx->info,
+						    ctx->preferred_pack_idx, 1,
 						    cur_fanout);
 
 		midx_fanout_sort(&fanout);
@@ -356,17 +345,16 @@ static struct pack_midx_entry *get_sorted_entries(struct multi_pack_index *m,
 						&fanout.entries[cur_object].oid))
 				continue;
 
-			ALLOC_GROW(deduplicated_entries, st_add(*nr_objects, 1),
+			ALLOC_GROW(ctx->entries, st_add(ctx->entries_nr, 1),
 				   alloc_objects);
-			memcpy(&deduplicated_entries[*nr_objects],
+			memcpy(&ctx->entries[ctx->entries_nr],
 			       &fanout.entries[cur_object],
 			       sizeof(struct pack_midx_entry));
-			(*nr_objects)++;
+			ctx->entries_nr++;
 		}
 	}
 
 	free(fanout.entries);
-	return deduplicated_entries;
 }
 
 static int write_midx_pack_names(struct hashfile *f, void *data)
@@ -886,6 +874,43 @@ static struct multi_pack_index *lookup_multi_pack_index(struct repository *r,
 	return result;
 }
 
+static int fill_packs_from_midx(struct write_midx_context *ctx,
+				const char *preferred_pack_name, uint32_t flags)
+{
+	uint32_t i;
+
+	for (i = 0; i < ctx->m->num_packs; i++) {
+		if (!should_include_pack(ctx, ctx->m->pack_names[i], 0))
+			continue;
+
+		ALLOC_GROW(ctx->info, ctx->nr + 1, ctx->alloc);
+
+		if (flags & MIDX_WRITE_REV_INDEX || preferred_pack_name) {
+			/*
+			 * If generating a reverse index, need to have
+			 * packed_git's loaded to compare their
+			 * mtimes and object count.
+			 *
+			 *
+			 * If a preferred pack is specified, need to
+			 * have packed_git's loaded to ensure the chosen
+			 * preferred pack has a non-zero object count.
+			 */
+			if (prepare_midx_pack(the_repository, ctx->m, i))
+				return error(_("could not load pack"));
+
+			if (open_pack_index(ctx->m->packs[i]))
+				die(_("could not open index for %s"),
+				    ctx->m->packs[i]->pack_name);
+		}
+
+		fill_pack_info(&ctx->info[ctx->nr++], ctx->m->packs[i],
+			       ctx->m->pack_names[i], i);
+	}
+
+	return 0;
+}
+
 static int write_midx_internal(const char *object_dir,
 			       struct string_list *packs_to_include,
 			       struct string_list *packs_to_drop,
@@ -895,7 +920,7 @@ static int write_midx_internal(const char *object_dir,
 {
 	struct strbuf midx_name = STRBUF_INIT;
 	unsigned char midx_hash[GIT_MAX_RAWSZ];
-	uint32_t i;
+	uint32_t i, start_pack;
 	struct hashfile *f = NULL;
 	struct lock_file lk;
 	struct write_midx_context ctx = { 0 };
@@ -912,15 +937,7 @@ static int write_midx_internal(const char *object_dir,
 		die_errno(_("unable to create leading directories of %s"),
 			  midx_name.buf);
 
-	if (!packs_to_include) {
-		/*
-		 * Only reference an existing MIDX when not filtering which
-		 * packs to include, since all packs and objects are copied
-		 * blindly from an existing MIDX if one is present.
-		 */
-		ctx.m = lookup_multi_pack_index(the_repository, object_dir);
-	}
-
+	ctx.m = lookup_multi_pack_index(the_repository, object_dir);
 	if (ctx.m && !midx_checksum_valid(ctx.m)) {
 		warning(_("ignoring existing multi-pack-index; checksum mismatch"));
 		ctx.m = NULL;
@@ -929,42 +946,23 @@ static int write_midx_internal(const char *object_dir,
 	ctx.nr = 0;
 	ctx.alloc = ctx.m ? ctx.m->num_packs : 16;
 	ctx.info = NULL;
+	ctx.to_include = packs_to_include;
 	ALLOC_ARRAY(ctx.info, ctx.alloc);
 
-	if (ctx.m) {
-		for (i = 0; i < ctx.m->num_packs; i++) {
-			ALLOC_GROW(ctx.info, ctx.nr + 1, ctx.alloc);
-
-			if (flags & MIDX_WRITE_REV_INDEX) {
-				/*
-				 * If generating a reverse index, need to have
-				 * packed_git's loaded to compare their
-				 * mtimes and object count.
-				 */
-				if (prepare_midx_pack(the_repository, ctx.m, i)) {
-					error(_("could not load pack"));
-					result = 1;
-					goto cleanup;
-				}
-
-				if (open_pack_index(ctx.m->packs[i]))
-					die(_("could not open index for %s"),
-					    ctx.m->packs[i]->pack_name);
-			}
-
-			fill_pack_info(&ctx.info[ctx.nr++], ctx.m->packs[i],
-				       ctx.m->pack_names[i], i);
-		}
+	if (ctx.m && fill_packs_from_midx(&ctx, preferred_pack_name,
+					  flags) < 0) {
+		result = 1;
+		goto cleanup;
 	}
 
+	start_pack = ctx.nr;
+
 	ctx.pack_paths_checked = 0;
 	if (flags & MIDX_PROGRESS)
 		ctx.progress = start_delayed_progress(_("Adding packfiles to multi-pack-index"), 0);
 	else
 		ctx.progress = NULL;
 
-	ctx.to_include = packs_to_include;
-
 	for_each_file_in_pack_dir(object_dir, add_pack_to_midx, &ctx);
 	stop_progress(&ctx.progress);
 
@@ -1054,8 +1052,7 @@ static int write_midx_internal(const char *object_dir,
 		}
 	}
 
-	ctx.entries = get_sorted_entries(ctx.m, ctx.info, ctx.nr, &ctx.entries_nr,
-					 ctx.preferred_pack_idx);
+	compute_sorted_entries(&ctx, start_pack);
 
 	ctx.large_offsets_needed = 0;
 	for (i = 0; i < ctx.entries_nr; i++) {

midx.c

@@ -25,13 +25,15 @@ const unsigned char *get_midx_checksum(struct multi_pack_index *m)
 
 void get_midx_filename(struct strbuf *out, const char *object_dir)
 {
-	strbuf_addf(out, "%s/pack/multi-pack-index", object_dir);
+	get_midx_filename_ext(out, object_dir, NULL, NULL);
 }
 
-void get_midx_rev_filename(struct strbuf *out, struct multi_pack_index *m)
+void get_midx_filename_ext(struct strbuf *out, const char *object_dir,
+			   const unsigned char *hash, const char *ext)
 {
-	get_midx_filename(out, m->object_dir);
-	strbuf_addf(out, "-%s.rev", hash_to_hex(get_midx_checksum(m)));
+	strbuf_addf(out, "%s/pack/multi-pack-index", object_dir);
+	if (ext)
+		strbuf_addf(out, "-%s.%s", hash_to_hex(hash), ext);
 }
 
 static int midx_read_oid_fanout(const unsigned char *chunk_start,

midx.h

@@ -74,9 +74,13 @@ struct multi_pack_index {
 #define MIDX_WRITE_BITMAP_HASH_CACHE (1 << 3)
 #define MIDX_WRITE_BITMAP_LOOKUP_TABLE (1 << 4)
 
+#define MIDX_EXT_REV "rev"
+#define MIDX_EXT_BITMAP "bitmap"
+
 const unsigned char *get_midx_checksum(struct multi_pack_index *m);
 void get_midx_filename(struct strbuf *out, const char *object_dir);
-void get_midx_rev_filename(struct strbuf *out, struct multi_pack_index *m);
+void get_midx_filename_ext(struct strbuf *out, const char *object_dir,
+			   const unsigned char *hash, const char *ext);
 
 struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local);
 int prepare_midx_pack(struct repository *r, struct multi_pack_index *m, uint32_t pack_int_id);

pack-bitmap.c

@@ -309,9 +309,8 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)
 char *midx_bitmap_filename(struct multi_pack_index *midx)
 {
 	struct strbuf buf = STRBUF_INIT;
-
-	get_midx_filename(&buf, midx->object_dir);
-	strbuf_addf(&buf, "-%s.bitmap", hash_to_hex(get_midx_checksum(midx)));
+	get_midx_filename_ext(&buf, midx->object_dir, get_midx_checksum(midx),
+			      MIDX_EXT_BITMAP);
 
 	return strbuf_detach(&buf, NULL);
 }

pack-revindex.c

@@ -381,7 +381,8 @@ int load_midx_revindex(struct multi_pack_index *m)
 	trace2_data_string("load_midx_revindex", the_repository,
 			   "source", "rev");
 
-	get_midx_rev_filename(&revindex_name, m);
+	get_midx_filename_ext(&revindex_name, m->object_dir,
+			      get_midx_checksum(m), MIDX_EXT_REV);
 
 	ret = load_revindex_from_disk(revindex_name.buf,
 				      m->num_objects,

t/t5319-multi-pack-index.sh

@@ -350,6 +350,29 @@ test_expect_success 'preferred packs must be non-empty' '
 	)
 '
 
+test_expect_success 'preferred pack from existing MIDX without bitmaps' '
+	git init preferred-without-bitmaps &&
+	(
+		cd preferred-without-bitmaps &&
+
+		test_commit one &&
+		pack="$(git pack-objects --all $objdir/pack/pack </dev/null)" &&
+
+		git multi-pack-index write &&
+
+		# make another pack so that the subsequent MIDX write
+		# has something to do
+		test_commit two &&
+		git repack -d &&
+
+		# write a new MIDX without bitmaps reusing the singular
+		# pack from the existing MIDX as the preferred pack in
+		# the new MIDX
+		git multi-pack-index write --preferred-pack=pack-$pack.pack
+	)
+
+'
+
 test_expect_success 'verify multi-pack-index success' '
 	git multi-pack-index verify --object-dir=$objdir
 '