4 files changed, 35 insertions, 13 deletions

diff --git a/source/shared.c b/source/shared.c
index 1b610a0..78dc3f4 100644
--- a/source/shared.c
+++ b/source/shared.c
@@ -451,11 +451,24 @@ int cgit_diff_files(const struct object_id *old_oid, const struct object_id *new
 	return 0;
 }
 
+void cgit_diff_limit_path(struct diff_options *opt, const char *prefix)
+{
+	struct pathspec_item *item;
+
+	item = xcalloc(1, sizeof(*item));
+	item->match = xstrdup(prefix);
+	item->len = strlen(prefix);
+	// nowildcard_len matching len makes git treat the path as literal
+	// rather than as a glob.
+	item->nowildcard_len = item->len;
+	opt->pathspec.nr = 1;
+	opt->pathspec.items = item;
+}
+
 void cgit_diff_tree(const struct object_id *old_oid, const struct object_id *new_oid,
 	filepair_fn fn, const char *prefix, int ignorews)
 {
 	struct diff_options opt;
-	struct pathspec_item *item;
 
 	repo_diff_setup(the_repository, &opt);
 	opt.output_format = DIFF_FORMAT_CALLBACK;
@@ -466,16 +479,8 @@ void cgit_diff_tree(const struct object_id *old_oid, const struct object_id *new
 		DIFF_XDL_SET(&opt, IGNORE_WHITESPACE);
 	opt.format_callback = cgit_diff_tree_cb;
 	opt.format_callback_data = fn;
-	if (prefix) {
-		item = xcalloc(1, sizeof(*item));
-		item->match = xstrdup(prefix);
-		item->len = strlen(prefix);
-		// nowildcard_len matching len makes git treat the path as
-		// literal rather than as a glob.
-		item->nowildcard_len = item->len;
-		opt.pathspec.nr = 1;
-		opt.pathspec.items = item;
-	}
+	if (prefix)
+		cgit_diff_limit_path(&opt, prefix);
 	diff_setup_done(&opt);
 
 	if (old_oid && !is_null_oid(old_oid))
diff --git a/source/shared.h b/source/shared.h
index 9e39389..d61c1f1 100644
--- a/source/shared.h
+++ b/source/shared.h
@@ -60,6 +60,11 @@ extern int cgit_diff_files(const struct object_id *old_oid, const struct object_
 	unsigned long *old_size, unsigned long *new_size, int *binary, int context, int ignorews,
 	linediff_fn fn);
 
+/*
+ * Limit a diff to the paths below prefix, which is taken literally.
+ */
+extern void cgit_diff_limit_path(struct diff_options *opt, const char *prefix);
+
 extern void cgit_diff_tree(const struct object_id *old_oid, const struct object_id *new_oid,
 	filepair_fn fn, const char *prefix, int ignorews);
 extern void cgit_diff_commit(struct commit *commit, filepair_fn fn, const char *prefix);
diff --git a/source/ui-diff.c b/source/ui-diff.c
index 5c9cd1c..a5202b5 100644
--- a/source/ui-diff.c
+++ b/source/ui-diff.c
@@ -535,13 +535,16 @@ static void filepair_cb(struct diff_filepair *pair)
 	end_file();
 }
 
-static void print_raw_patch(const struct object_id *old_tree_oid, const struct object_id *new_tree_oid)
+static void print_raw_patch(const struct object_id *old_tree_oid, const struct object_id *new_tree_oid,
+	const char *prefix)
 {
 	struct diff_options diffopt;
 
 	repo_diff_setup(the_repository, &diffopt);
 	diffopt.output_format = DIFF_FORMAT_PATCH;
 	diffopt.flags.recursive = 1;
+	if (prefix)
+		cgit_diff_limit_path(&diffopt, prefix);
 	diff_setup_done(&diffopt);
 
 	ctx.page.mimetype = "text/plain";
@@ -683,7 +686,7 @@ void cgit_print_diff(const char *new_rev, const char *old_rev, const char *prefi
 	cap_diffs = !path || prefix_is_dir(old_tree_oid, new_tree_oid, path);
 
 	if (raw) {
-		print_raw_patch(old_tree_oid, new_tree_oid);
+		print_raw_patch(old_tree_oid, new_tree_oid, path);
 		return;
 	}
 
diff --git a/tests/t0108-rawdiff.sh b/tests/t0108-rawdiff.sh
index 7753bdb..f68628a 100755
--- a/tests/t0108-rawdiff.sh
+++ b/tests/t0108-rawdiff.sh
@@ -46,4 +46,13 @@ test_expect_success 'compare with output of git-diff(1)' '
 	cmp tmp_ tmp2
 '
 
+test_expect_success 'a path limits the diff to that file' '
+	cgit_query "url=foo/rawdiff/file-4&id=$id&id2=$id2" >tmp &&
+	git --git-dir="$PWD/repos/foo/.git" diff HEAD~3..HEAD -- file-4 >tmp2 &&
+	strip_headers <tmp >tmp_ &&
+	cmp tmp_ tmp2 &&
+	grep "file-4" tmp_ &&
+	! grep "file-5" tmp_
+'
+
 test_done