replace: make sure --edit results in a different object

It's a bad idea to create a replace ref for an object
that points to the original object itself.

That's why we have to check if the result from editing
the original object is a different object and error out
if it isn't.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/replace.c b/builtin/replace.c
index 3da1bae0a60942f3aad5362f12a4e1db42589f32..07518040395139e9e159617bd7c2da548237bbbf 100644 (file)
--- a/builtin/replace.c
+++ b/builtin/replace.c
@@ -275,6 +275,9 @@ static int edit_and_replace(const char *object_ref, int force)
 
        free(tmpfile);
 
+       if (!hashcmp(old, new))
+               return error("new object is the same as the old one: '%s'", sha1_to_hex(old));
+
        return replace_object_sha1(object_ref, old, "replacement", new, force);
 }