builtin/mv: refactor add_slash() to always return allocated strings

The `add_slash()` function will only conditionally return an allocated
string when the passed-in string did not yet have a trailing slash. This
makes the memory ownership harder to track than really necessary.

It's dubious whether this optimization really buys us all that much. The
number of times we execute this function is bounded by the number of
arguments to git-mv(1), so in the typical case we may end up saving an
allocation or two.

Simplify the code to unconditionally return allocated strings.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

builtin/mv.c

@@ -76,7 +76,7 @@ static const char **internal_prefix_pathspec(const char *prefix,
 	return result;
 }
 
-static const char *add_slash(const char *path)
+static char *add_slash(const char *path)
 {
 	size_t len = strlen(path);
 	if (len && path[len - 1] != '/') {
@@ -86,7 +86,7 @@ static const char *add_slash(const char *path)
 		with_slash[len] = 0;
 		return with_slash;
 	}
-	return path;
+	return xstrdup(path);
 }
 
 #define SUBMODULE_WITH_GITDIR ((const char *)1)
@@ -111,7 +111,7 @@ static void prepare_move_submodule(const char *src, int first,
 static int index_range_of_same_dir(const char *src, int length,
 				   int *first_p, int *last_p)
 {
-	const char *src_w_slash = add_slash(src);
+	char *src_w_slash = add_slash(src);
 	int first, last, len_w_slash = length + 1;
 
 	first = index_name_pos(the_repository->index, src_w_slash, len_w_slash);
@@ -124,8 +124,8 @@ static int index_range_of_same_dir(const char *src, int length,
 		if (strncmp(path, src_w_slash, len_w_slash))
 			break;
 	}
-	if (src_w_slash != src)
-		free((char *)src_w_slash);
+
+	free(src_w_slash);
 	*first_p = first;
 	*last_p = last;
 	return last - first;
@@ -141,7 +141,7 @@ static int index_range_of_same_dir(const char *src, int length,
 static int empty_dir_has_sparse_contents(const char *name)
 {
 	int ret = 0;
-	const char *with_slash = add_slash(name);
+	char *with_slash = add_slash(name);
 	int length = strlen(with_slash);
 
 	int pos = index_name_pos(the_repository->index, with_slash, length);
@@ -159,8 +159,7 @@ static int empty_dir_has_sparse_contents(const char *name)
 	}
 
 free_return:
-	if (with_slash != name)
-		free((char *)with_slash);
+	free(with_slash);
 	return ret;
 }
 
@@ -178,7 +177,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 		OPT_END(),
 	};
 	const char **source, **destination, **dest_path, **submodule_gitfile;
-	const char *dst_w_slash;
+	char *dst_w_slash = NULL;
 	const char **src_dir = NULL;
 	int src_dir_nr = 0, src_dir_alloc = 0;
 	struct strbuf a_src_dir = STRBUF_INIT;
@@ -243,10 +242,6 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 				dst_mode = SPARSE;
 		}
 	}
-	if (dst_w_slash != dest_path[0]) {
-		free((char *)dst_w_slash);
-		dst_w_slash = NULL;
-	}
 
 	/* Checking */
 	for (i = 0; i < argc; i++) {
@@ -265,12 +260,14 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 
 			pos = index_name_pos(the_repository->index, src, length);
 			if (pos < 0) {
-				const char *src_w_slash = add_slash(src);
+				char *src_w_slash = add_slash(src);
 				if (!path_in_sparse_checkout(src_w_slash, the_repository->index) &&
 				    empty_dir_has_sparse_contents(src)) {
+					free(src_w_slash);
 					modes[i] |= SKIP_WORKTREE_DIR;
 					goto dir_check;
 				}
+				free(src_w_slash);
 				/* only error if existence is expected. */
 				if (!(modes[i] & SPARSE))
 					bad = _("bad source");
@@ -310,7 +307,9 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 
 dir_check:
 		if (S_ISDIR(st.st_mode)) {
-			int j, dst_len, n;
+			char *dst_with_slash;
+			size_t dst_with_slash_len;
+			int j, n;
 			int first = index_name_pos(the_repository->index, src, length), last;
 
 			if (first >= 0) {
@@ -335,19 +334,21 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 			REALLOC_ARRAY(modes, n);
 			REALLOC_ARRAY(submodule_gitfile, n);
 
-			dst = add_slash(dst);
-			dst_len = strlen(dst);
+			dst_with_slash = add_slash(dst);
+			dst_with_slash_len = strlen(dst_with_slash);
 
 			for (j = 0; j < last - first; j++) {
 				const struct cache_entry *ce = the_repository->index->cache[first + j];
 				const char *path = ce->name;
 				source[argc + j] = path;
 				destination[argc + j] =
-					prefix_path(dst, dst_len, path + length + 1);
+					prefix_path(dst_with_slash, dst_with_slash_len, path + length + 1);
 				memset(modes + argc + j, 0, sizeof(enum update_mode));
 				modes[argc + j] |= ce_skip_worktree(ce) ? SPARSE : INDEX;
 				submodule_gitfile[argc + j] = NULL;
 			}
+
+			free(dst_with_slash);
 			argc += last - first;
 			goto act_on_entry;
 		}
@@ -565,6 +566,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 			       COMMIT_LOCK | SKIP_IF_UNCHANGED))
 		die(_("Unable to write new index file"));
 
+	free(dst_w_slash);
 	string_list_clear(&src_for_dst, 0);
 	string_list_clear(&dirty_paths, 0);
 	UNLEAK(source);