git: update to v2.13.4

Update to git version v2.13.4: With commit 8aee769f (pathspec: copy and free
owned memory) the definition of struct pathspec_item has changed with the
expectation that pathspecs will be managed dynamically. We work around this
a bit by setting up a static structure, but let's allocate the match string
to avoid needing to cast away const.

Updated a patch from John Keeping <john@keeping.me.uk> for git v2.12.1.

Makefile

@@ -14,7 +14,7 @@ htmldir = $(docdir)
 pdfdir = $(docdir)
 mandir = $(prefix)/share/man
 SHA1_HEADER = <openssl/sha.h>
-GIT_VER = 2.11.0
+GIT_VER = 2.13.4
 GIT_URL = https://www.kernel.org/pub/software/scm/git/git-$(GIT_VER).tar.gz
 INSTALL = install
 COPYTREE = cp -r

git

@@ -1 +1 @@
-Subproject commit 454cb6bd52a4de614a3633e4f547af03d5c3b640
+Subproject commit cf8899d285d2648013040ec7196ffd3de0606664

shared.c

@@ -352,7 +352,7 @@ void cgit_diff_tree(const struct object_id *old_oid,
 	opt.format_callback = cgit_diff_tree_cb;
 	opt.format_callback_data = fn;
 	if (prefix) {
-		item.match = prefix;
+		item.match = xstrdup(prefix);
 		item.len = strlen(prefix);
 		opt.pathspec.nr = 1;
 		opt.pathspec.items = &item;
@@ -365,6 +365,8 @@ void cgit_diff_tree(const struct object_id *old_oid,
 		diff_root_tree_sha1(new_oid->hash, "", &opt);
 	diffcore_std(&opt);
 	diff_flush(&opt);
+
+	free(item.match);
 }
 
 void cgit_diff_commit(struct commit *commit, filepair_fn fn, const char *prefix)

ui-blob.c

@@ -38,7 +38,7 @@ int cgit_ref_path_exists(const char *path, const char *ref, int file_only)
 	struct object_id oid;
 	unsigned long size;
 	struct pathspec_item path_items = {
-		.match = path,
+		.match = xstrdup(path),
 		.len = strlen(path)
 	};
 	struct pathspec paths = {
@@ -53,10 +53,13 @@ int cgit_ref_path_exists(const char *path, const char *ref, int file_only)
 	};
 
 	if (get_oid(ref, &oid))
-		return 0;
+		goto done;
 	if (sha1_object_info(oid.hash, &size) != OBJ_COMMIT)
-		return 0;
+		goto done;
 	read_tree_recursive(lookup_commit_reference(oid.hash)->tree, "", 0, 0, &paths, walk_tree, &walk_tree_ctx);
+
+done:
+	free(path_items.match);
 	return walk_tree_ctx.found_path;
 }