midx: clear midx on repack

If a 'git repack' command replaces existing packfiles, then we must
clear the existing multi-pack-index before moving the packfiles it
references.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/repack.c

@@ -8,6 +8,7 @@
 #include "strbuf.h"
 #include "string-list.h"
 #include "argv-array.h"
+#include "midx.h"
 
 static int delta_base_offset = 1;
 static int pack_kept_objects = -1;
@@ -174,6 +175,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	int no_update_server_info = 0;
 	int quiet = 0;
 	int local = 0;
+	int midx_cleared = 0;
 
 	struct option builtin_repack_options[] = {
 		OPT_BIT('a', NULL, &pack_everything,
@@ -333,6 +335,13 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	for_each_string_list_item(item, &names) {
 		for (ext = 0; ext < ARRAY_SIZE(exts); ext++) {
 			char *fname, *fname_old;
+
+			if (!midx_cleared) {
+				/* if we move a packfile, it will invalidated the midx */
+				clear_midx_file(get_object_directory());
+				midx_cleared = 1;
+			}
+
 			fname = mkpathdup("%s/pack-%s%s", packdir,
 						item->string, exts[ext].name);
 			if (!file_exists(fname)) {

midx.c

@@ -904,3 +904,15 @@ int write_midx_file(const char *object_dir)
 	free(midx_name);
 	return 0;
 }
+
+void clear_midx_file(const char *object_dir)
+{
+	char *midx = get_midx_filename(object_dir);
+
+	if (remove_path(midx)) {
+		UNLEAK(midx);
+		die(_("failed to clear multi-pack-index at %s"), midx);
+	}
+
+	free(midx);
+}

midx.h

@@ -39,5 +39,6 @@ int midx_contains_pack(struct multi_pack_index *m, const char *idx_name);
 int prepare_multi_pack_index_one(struct repository *r, const char *object_dir);
 
 int write_midx_file(const char *object_dir);
+void clear_midx_file(const char *object_dir);
 
 #endif

t/t5319-multi-pack-index.sh

@@ -141,6 +141,15 @@ test_expect_success 'write midx with twelve packs' '
 
 compare_results_with_midx "twelve packs"
 
+test_expect_success 'repack removes multi-pack-index' '
+	test_path_is_file $objdir/pack/multi-pack-index &&
+	git repack -adf &&
+	test_path_is_missing $objdir/pack/multi-pack-index
+'
+
+compare_results_with_midx "after repack"
+
+
 # usage: corrupt_data <file> <pos> [<data>]
 corrupt_data () {
 	file=$1