3 files changed, 11 insertions, 5 deletions

diff --git a/cgit.h b/cgit.h
index e3d9cb8..5ef0bc5 100644
--- a/cgit.h
+++ b/cgit.h
@@ -167,13 +167,13 @@ extern void *cgit_free_commitinfo(struct commitinfo *info);
 extern int cgit_diff_files(const unsigned char *old_sha1,
 			   const unsigned char *new_sha1,
 			   linediff_fn fn);
 
 extern void cgit_diff_tree(const unsigned char *old_sha1,
 			   const unsigned char *new_sha1,
-			   filepair_fn fn);
+			   filepair_fn fn, const char *prefix);
 
 extern void cgit_diff_commit(struct commit *commit, filepair_fn fn);
 
 extern char *fmt(const char *format,...);
 
 extern void html(const char *txt);
diff --git a/shared.c b/shared.c
index 0a6a5ed..3d4feea 100644
--- a/shared.c
+++ b/shared.c
@@ -383,24 +383,31 @@ int cgit_diff_files(const unsigned char *old_sha1,
 	xdl_diff(&file1, &file2, &diff_params, &emit_params, &emit_cb);
 	return 0;
 }
 
 void cgit_diff_tree(const unsigned char *old_sha1,
 		    const unsigned char *new_sha1,
-		    filepair_fn fn)
+		    filepair_fn fn, const char *prefix)
 {
 	struct diff_options opt;
 	int ret;
+	int prefixlen;
 
 	diff_setup(&opt);
 	opt.output_format = DIFF_FORMAT_CALLBACK;
 	opt.detect_rename = 1;
 	opt.rename_limit = cgit_renamelimit;
 	opt.recursive = 1;
 	opt.format_callback = cgit_diff_tree_cb;
 	opt.format_callback_data = fn;
+	if (prefix) {
+		opt.nr_paths = 1;
+		opt.paths = &prefix;
+		prefixlen = strlen(prefix);
+		opt.pathlens = &prefixlen;
+	}
 	diff_setup_done(&opt);
 
 	if (old_sha1 && !is_null_sha1(old_sha1))
 		ret = diff_tree_sha1(old_sha1, new_sha1, "", &opt);
 	else
 		ret = diff_root_tree_sha1(new_sha1, "", &opt);
@@ -411,8 +418,8 @@ void cgit_diff_tree(const unsigned char *old_sha1,
 void cgit_diff_commit(struct commit *commit, filepair_fn fn)
 {
 	unsigned char *old_sha1 = NULL;
 
 	if (commit->parents)
 		old_sha1 = commit->parents->item->object.sha1;
-	cgit_diff_tree(old_sha1, commit->object.sha1, fn);
+	cgit_diff_tree(old_sha1, commit->object.sha1, fn, NULL);
 }
diff --git a/ui-diff.c b/ui-diff.c
index 0be845f..11a2ff8 100644
--- a/ui-diff.c
+++ b/ui-diff.c
@@ -128,13 +128,12 @@ void cgit_print_diff(const char *new_rev, const char *old_rev)
 			return;
 		}
 		commit2 = lookup_commit_reference(sha2);
 		if (!commit2 || parse_commit(commit2))
 			cgit_print_error(fmt("Bad commit: %s", sha1_to_hex(sha2)));
 	}
-
 	html("<table class='diff'>");
 	html("<tr><td>");
-	cgit_diff_tree(sha2, sha1, filepair_cb);
+	cgit_diff_tree(sha2, sha1, filepair_cb, NULL);
 	html("</td></tr>");
 	html("</table>");
 }