[PATCH] Do not use ctime if file mode is not used

[Alex Riesen <raa.lkml@gmail.com>]

On some file systems, the only part of inode information we need
(executable) cannot be used, so ctime can be ignored as well. Change
time is updated when file attributes were changed (or it is written
to, but in this case, mtime is updated as well).

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
---

Junio C Hamano, Wed, Jul 23, 2008 02:12:50 +0200:
> > I had that at first (NO_DEPENDABLE_CTIME, than IGNORE_CTIME), than
> > deemed it excessive.
> 
> Why is it excessive?  My initial reaction was "what does trustable
> filemode nor trust_executable_bit has anything to do with ctime".  Please
> explain.

You know, you have a good point... (and I'm sometimes really stupid)
Of course it depends on the underlying filesystem!

The updated patch is untested yet, but should be obviously correct.

BTW, any idea how to check if all callers of ce_match_stat_basic have
read the configuration? It is not that essential to have
trust_executable_bit set correctly, though. In worst case an index
entry will be marked not up-to-date.

 read-cache.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/read-cache.c b/read-cache.c
index a50a851..f2fa0d9 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -181,7 +181,7 @@ static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 	}
 	if (ce->ce_mtime != (unsigned int) st->st_mtime)
 		changed |= MTIME_CHANGED;
-	if (ce->ce_ctime != (unsigned int) st->st_ctime)
+	if (trust_executable_bit && ce->ce_ctime != (unsigned int) st->st_ctime)
 		changed |= CTIME_CHANGED;
 
 	if (ce->ce_uid != (unsigned int) st->st_uid ||
-- 
1.6.0.rc0.70.g5aae9