WIP

Author: ttaylorr

builtin/multi-pack-index.c

@@ -61,6 +61,7 @@ static char const * const builtin_multi_pack_index_usage[] = {
 static struct opts_multi_pack_index {
 	char *object_dir;
 	const char *preferred_pack;
+	const char *incremental_base;
 	char *refs_snapshot;
 	unsigned long batch_size;
 	unsigned flags;
@@ -214,6 +215,8 @@ static int cmd_multi_pack_index_compact(int argc, const char **argv,
 
 	struct option *options;
 	static struct option builtin_multi_pack_index_compact_options[] = {
+		OPT_STRING(0, "base", &opts.incremental_base, N_("checksum"),
+			   N_("base MIDX for incremental writes")),
 		OPT_BIT(0, "bitmap", &opts.flags, N_("write multi-pack bitmap"),
 			MIDX_WRITE_BITMAP | MIDX_WRITE_REV_INDEX),
 		OPT_BIT(0, "incremental", &opts.flags,
@@ -258,7 +261,8 @@ static int cmd_multi_pack_index_compact(int argc, const char **argv,
 	if (!to_midx)
 		die(_("could not find MIDX 'to': %s"), argv[1]);
 
-	return write_midx_file_compact(source, from_midx, to_midx, opts.flags);
+	return write_midx_file_compact(source, from_midx, to_midx,
+				       opts.incremental_base, opts.flags);
 }
 
 static int cmd_multi_pack_index_verify(int argc, const char **argv,

midx-write.c

@@ -1157,6 +1157,7 @@ struct write_midx_opts {
 
 	const char *preferred_pack_name;
 	const char *refs_snapshot;
+	const char *incremental_base;
 	unsigned flags;
 };
 
@@ -1196,6 +1197,9 @@ static int write_midx_internal(struct write_midx_opts *opts)
 
 		ctx.compact_from = opts->compact_from;
 		ctx.compact_to = opts->compact_to;
+	} else if (opts->incremental_base) {
+		error(_("custom bases are only supported during compaction"));
+		goto cleanup;
 	}
 
 	if (ctx.incremental)
@@ -1231,11 +1235,28 @@ static int write_midx_internal(struct write_midx_opts *opts)
 
 	/*
 	 * If compacting MIDX layer(s) in the range [from, to], then the
-	 * compacted MIDX will share the same base MIDX as 'from'.
+	 * compacted MIDX will share the same base MIDX as 'from',
+	 * unless a custom --base is specified (see below).
 	 */
 	if (ctx.compact)
 		ctx.base_midx = ctx.compact_from->base_midx;
 
+	if (opts->incremental_base) {
+		while (ctx.base_midx) {
+			if (!strcmp(opts->incremental_base,
+				    get_midx_checksum(ctx.base_midx)))
+				break;
+
+			ctx.base_midx = ctx.base_midx->base_midx;
+		}
+
+		if (!ctx.base_midx) {
+			error(_("could not find base MIDX '%s'"),
+			      opts->incremental_base);
+			goto cleanup;
+		}
+	}
+
 	ctx.nr = 0;
 	ctx.alloc = ctx.m ? ctx.m->num_packs + ctx.m->num_packs_in_base : 16;
 	ctx.info = NULL;
@@ -1757,12 +1778,14 @@ int write_midx_file_only(struct odb_source *source,
 int write_midx_file_compact(struct odb_source *source,
 			    struct multi_pack_index *from,
 			    struct multi_pack_index *to,
+			    const char *incremental_base,
 			    unsigned flags)
 {
 	struct write_midx_opts opts = {
 		.source = source,
 		.compact_from = from,
 		.compact_to = to,
+		.incremental_base = incremental_base,
 		.flags = flags | MIDX_WRITE_COMPACT,
 	};
 

midx.h

@@ -134,6 +134,7 @@ int write_midx_file_only(struct odb_source *source,
 int write_midx_file_compact(struct odb_source *source,
 			    struct multi_pack_index *from,
 			    struct multi_pack_index *to,
+			    const char *incremental_base,
 			    unsigned flags);
 void clear_midx_file(struct repository *r);
 int verify_midx_file(struct odb_source *source, unsigned flags);

t/t5335-compact-multi-pack-index.sh

@@ -197,4 +197,28 @@ test_expect_success 'MIDX compaction with bitmaps (non-trivial)' '
 	)
 '
 
+test_expect_success 'MIDX compaction with --base' '
+	git init midx-compact-with--base &&
+	(
+		cd midx-compact-with--base &&
+
+		write_packs A B C D &&
+
+		test_line_count = 4 $midx_chain &&
+
+		cp "$midx_chain" "$midx_chain".bak &&
+
+		git multi-pack-index compact --incremental \
+			--base="$(nth_line 1 "$midx_chain")" \
+			"$(nth_line 3 "$midx_chain")" \
+			"$(nth_line 4 "$midx_chain")" &&
+		test_line_count = 2 $midx_chain &&
+
+		head -n1 "$midx_chain.bak" >actual &&
+		head -n1 "$midx_chain" >expect &&
+
+		test_cmp expect actual
+	)
+'
+
 test_done