diff: handle relative paths in no-index

When diff-no-index is given a relative path to a file outside the
repository, it aborts with error. However, if the file is given
using an absolute path, the diff runs as expected. The two cases
should be treated the same.

Tests and commit message by Tim Henigan.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Tim Henigan <tim.henigan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -455,6 +455,7 @@ extern const char *prefix_filename(const char *prefix, int len, const char *path
 extern int check_filename(const char *prefix, const char *name);
 extern void verify_filename(const char *prefix, const char *name);
 extern void verify_non_filename(const char *prefix, const char *name);
+extern int path_inside_repo(const char *prefix, const char *path);
 
 #define INIT_DB_QUIET 0x0001
 

diff-no-index.c

@@ -151,23 +151,6 @@ static int queue_diff(struct diff_options *o,
 	}
 }
 
-static int path_outside_repo(const char *path)
-{
-	const char *work_tree;
-	size_t len;
-
-	if (!is_absolute_path(path))
-		return 0;
-	work_tree = get_git_work_tree();
-	if (!work_tree)
-		return 1;
-	len = strlen(work_tree);
-	if (strncmp(path, work_tree, len) ||
-	    (path[len] != '\0' && path[len] != '/'))
-		return 1;
-	return 0;
-}
-
 void diff_no_index(struct rev_info *revs,
 		   int argc, const char **argv,
 		   int nongit, const char *prefix)
@@ -197,8 +180,8 @@ void diff_no_index(struct rev_info *revs,
 		 * a colourful "diff" replacement.
 		 */
 		if ((argc != i + 2) ||
-		    (!path_outside_repo(argv[i]) &&
-		     !path_outside_repo(argv[i+1])))
+		    (path_inside_repo(prefix, argv[i]) &&
+		     path_inside_repo(prefix, argv[i+1])))
 			return;
 	}
 	if (argc != i + 2)

setup.c

@@ -4,7 +4,7 @@
 static int inside_git_dir = -1;
 static int inside_work_tree = -1;
 
-char *prefix_path(const char *prefix, int len, const char *path)
+static char *prefix_path_gently(const char *prefix, int len, const char *path)
 {
 	const char *orig = path;
 	char *sanitized;
@@ -31,7 +31,8 @@ char *prefix_path(const char *prefix, int len, const char *path)
 		if (strncmp(sanitized, work_tree, len) ||
 		    (len > root_len && sanitized[len] != '\0' && sanitized[len] != '/')) {
 		error_out:
-			die("'%s' is outside repository", orig);
+			free(sanitized);
+			return NULL;
 		}
 		if (sanitized[len] == '/')
 			len++;
@@ -40,6 +41,25 @@ char *prefix_path(const char *prefix, int len, const char *path)
 	return sanitized;
 }
 
+char *prefix_path(const char *prefix, int len, const char *path)
+{
+	char *r = prefix_path_gently(prefix, len, path);
+	if (!r)
+		die("'%s' is outside repository", path);
+	return r;
+}
+
+int path_inside_repo(const char *prefix, const char *path)
+{
+	int len = prefix ? strlen(prefix) : 0;
+	char *r = prefix_path_gently(prefix, len, path);
+	if (r) {
+		free(r);
+		return 1;
+	}
+	return 0;
+}
+
 int check_filename(const char *prefix, const char *arg)
 {
 	const char *name;

t/t4053-diff-no-index.sh

@@ -8,12 +8,25 @@ test_expect_success 'setup' '
 	mkdir a &&
 	mkdir b &&
 	echo 1 >a/1 &&
-	echo 2 >a/2
+	echo 2 >a/2 &&
+	git init repo &&
+	echo 1 >repo/a &&
+	mkdir -p non/git &&
+	echo 1 >non/git/a &&
+	echo 1 >non/git/b
 '
 
 test_expect_success 'git diff --no-index directories' '
 	git diff --no-index a b >cnt
 	test $? = 1 && test_line_count = 14 cnt
 '
 
+test_expect_success 'git diff --no-index relative path outside repo' '
+	(
+		cd repo &&
+		test_expect_code 0 git diff --no-index a ../non/git/a &&
+		test_expect_code 0 git diff --no-index ../non/git/a ../non/git/b
+	)
+'
+
 test_done