Don't die when diffing trees with subprojects

The subprojects needs special handling, since they refer to objects
which normally won't exist in the refering repository.

Fix some extended header bugs and missing features while at it.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

ui-diff.c

@@ -31,39 +31,63 @@ static void print_line(char *line, int len)
 	line[len-1] = c;
 }
 
-static void header(unsigned char *sha1, char *path1,
-		   unsigned char *sha2, char *path2)
+static void header(unsigned char *sha1, char *path1, int mode1,
+		   unsigned char *sha2, char *path2, int mode2)
 {
 	char *abbrev1, *abbrev2;
-	if (is_null_sha1(sha1))
-		path1 = "dev/null";
-	if (is_null_sha1(sha2))
-		path2 = "dev/null";
+	int subproject;
+
+	subproject = (S_ISDIRLNK(mode1) || S_ISDIRLNK(mode2));
 	html("<tr><td>");
 	html("<div class='head'>");
 	html("diff --git a/");
 	html_txt(path1);
 	html(" b/");
 	html_txt(path2);
-	abbrev1 = xstrdup(find_unique_abbrev(sha1, DEFAULT_ABBREV));
-	abbrev2 = xstrdup(find_unique_abbrev(sha2, DEFAULT_ABBREV));
-	htmlf("\nindex %s..%s", abbrev1, abbrev2);
-	free(abbrev1);
-	free(abbrev2);
-	html("\n--- a/");
-	html_txt(path1);
-	html("\n+++ b/");
-	html_txt(path2);
+
+	if (is_null_sha1(sha1))
+		path1 = "dev/null";
+	if (is_null_sha1(sha2))
+		path2 = "dev/null";
+
+	if (mode1 == 0)
+		htmlf("<br/>new file mode %.6o", mode2);
+
+	if (mode2 == 0)
+		htmlf("<br/>deleted file mode %.6o", mode1);
+
+	if (!subproject) {
+		abbrev1 = xstrdup(find_unique_abbrev(sha1, DEFAULT_ABBREV));
+		abbrev2 = xstrdup(find_unique_abbrev(sha2, DEFAULT_ABBREV));
+		htmlf("<br/>index %s..%s", abbrev1, abbrev2);
+		free(abbrev1);
+		free(abbrev2);
+		if (mode1 != 0 && mode2 != 0) {
+			htmlf(" %.6o", mode1);
+			if (mode2 != mode1)
+				htmlf("..%.6o", mode2);
+		}
+		html("<br/>--- a/");
+		html_txt(path1);
+		html("<br/>+++ b/");
+		html_txt(path2);
+	}
 	html("</div>");
 }
 
 static void filepair_cb(struct diff_filepair *pair)
 {
-	header(pair->one->sha1, pair->one->path,
-	       pair->two->sha1, pair->two->path);
+	header(pair->one->sha1, pair->one->path, pair->one->mode,
+	       pair->two->sha1, pair->two->path, pair->two->mode);
+	if (S_ISDIRLNK(pair->one->mode) || S_ISDIRLNK(pair->two->mode)) {
+		if (S_ISDIRLNK(pair->one->mode))
+			print_line(fmt("-Subproject %s", sha1_to_hex(pair->one->sha1)), 52);
+		if (S_ISDIRLNK(pair->two->mode))
+			print_line(fmt("+Subproject %s", sha1_to_hex(pair->two->sha1)), 52);
+		return;
+	}
 	if (cgit_diff_files(pair->one->sha1, pair->two->sha1, print_line))
 		cgit_print_error("Error running diff");
-	html("</tr></td>");
 }
 
 void cgit_print_diff(const char *head, const char *old_hex, const char *new_hex, char *path)
@@ -100,7 +124,7 @@ void cgit_print_diff(const char *head, const char *old_hex, const char *new_hex,
 	switch(type) {
 	case OBJ_BLOB:
 		html("<tr><td>");
-		header(sha1, path, sha2, path);
+		header(sha1, path, 0644, sha2, path, 0644);
 		if (cgit_diff_files(sha1, sha2, print_line))
 			cgit_print_error("Error running diff");
 		html("</tr></td>");