[PATCH 1/4] diff: further cleanup.

When preparing data to feed the external diff, we should give
the mode we obtained from the caller, even when we are dealing
with a file with 0{40} SHA1 (i.e. the caller said "look at the
filesystem"), since the mode passed by the caller via
diff_addremove() or diff_change() is always trustworthy.

This is _not_ a bugfix --- the existing code stat() on the file
ifself and does the same computation on st.st_mode to compute
the mode the same way the caller did to give the original mode.
We cannot remove the stat() call from here, but the extra
computation to create the mode value is unnecessary.

Signed-off-by: Junio C Hamano <redacted>
---
 diff.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

9c88ea020142346a56e36cea87e349814675f3f5 (from f96e0e2250f29f5ba2ae06c6b401a83fa1b828b4)

diff --git a/diff.c b/diff.c
--- a/diff.c
+++ b/diff.c

@@ -421,8 +421,13 @@ static void prepare_temp_file(const char
 				strcpy(temp->hex, sha1_to_hex(null_sha1));
 			else
 				strcpy(temp->hex, sha1_to_hex(one->sha1));
-			sprintf(temp->mode, "%06o",
-				S_IFREG |ce_permissions(st.st_mode));
+			/* Even though we may sometimes borrow the
+			 * contents from the work tree, we always want
+			 * one->mode.  mode is trustworthy even when
+			 * !(one->sha1_valid), as long as
+			 * DIFF_FILE_VALID(one).
+			 */
+			sprintf(temp->mode, "%06o", one->mode);
 		}
 		return;
 	}