git-diff: allow --no-index semantics a bit more

Even when inside a git work tree, if two paths are given and at least one
is clearly outside the work tree, it cannot be a request to diff a tracked
path anyway; allow such an invocation to use --no-index semantics.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/diff-no-index.c b/diff-no-index.c
index 1b57feeb2454b00686b4c1acee8d97e47223be8e..b1ae7912c18ee762d22b5530fba8ad39f2364315 100644 (file)
--- a/diff-no-index.c
+++ b/diff-no-index.c
@@ -144,6 +144,25 @@ static int queue_diff(struct diff_options *o,
        }
 }
 
+static int path_outside_repo(const char *path)
+{
+       /*
+        * We have already done setup_git_directory_gently() so we
+        * know we are inside a git work tree already.
+        */
+       const char *work_tree;
+       size_t len;
+
+       if (!is_absolute_path(path))
+               return 0;
+       work_tree = get_git_work_tree();
+       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)
@@ -162,13 +181,19 @@ void diff_no_index(struct rev_info *revs,
                        break;
        }
 
-       /*
-        * No explicit --no-index, but "git diff --opts A B" outside
-        * a git repository is a cute hack to support.
-        */
-       if (!no_index && !nongit)
-               return;
-
+       if (!no_index && !nongit) {
+               /*
+                * Inside a git repository, without --no-index.  Only
+                * when a path outside the repository is given,
+                * e.g. "git diff /var/tmp/[12]", or "git diff
+                * Makefile /var/tmp/Makefile", allow it to be used as
+                * a colourful "diff" replacement.
+                */
+               if ((argc != i + 2) ||
+                   (!path_outside_repo(argv[i]) &&
+                    !path_outside_repo(argv[i+1])))
+                       return;
+       }
        if (argc != i + 2)
                die("git diff %s takes two paths",
                    no_index ? "--no-index" : "[--no-index]");