[PATCH] Perform minimal stat comparison when some stat fields are not set

[Robin Rosenberg <robin.rosenberg@dewire.com>]

At least JGit does sets uid, gid, ctime, ino and dev fields to zero
on update. To Git this looks like the stat data does not match and
a full file compare will be forced even it size and mtime match. This
is in practice unnecessary. Sense JGit's presence by checking if ino
and dev is zero.

Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>
---
 read-cache.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/read-cache.c b/read-cache.c
index fda78bc..6f13a22 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -197,21 +197,26 @@ static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 	}
 	if (ce->ce_mtime.sec != (unsigned int)st->st_mtime)
 		changed |= MTIME_CHANGED;
-	if (trust_ctime && ce->ce_ctime.sec != (unsigned int)st->st_ctime)
+
+	int minimal_stat = (ce->ce_ino == 0 && ce->ce_dev == 0);
+
+	if (trust_ctime && !minimal_stat && ce->ce_ctime.sec != (unsigned int)st->st_ctime)
 		changed |= CTIME_CHANGED;
 
 #ifdef USE_NSEC
 	if (ce->ce_mtime.nsec != ST_MTIME_NSEC(*st))
 		changed |= MTIME_CHANGED;
-	if (trust_ctime && ce->ce_ctime.nsec != ST_CTIME_NSEC(*st))
+	if (trust_ctime && !minimal_stat && ce->ce_ctime.nsec != ST_CTIME_NSEC(*st))
 		changed |= CTIME_CHANGED;
 #endif
 
-	if (ce->ce_uid != (unsigned int) st->st_uid ||
-	    ce->ce_gid != (unsigned int) st->st_gid)
-		changed |= OWNER_CHANGED;
-	if (ce->ce_ino != (unsigned int) st->st_ino)
-		changed |= INODE_CHANGED;
+	if (!minimal_stat) {
+		if (ce->ce_uid != (unsigned int) st->st_uid ||
+			ce->ce_gid != (unsigned int) st->st_gid)
+			changed |= OWNER_CHANGED;
+		if (ce->ce_ino != 0 && ce->ce_ino != (unsigned int) st->st_ino)
+			changed |= INODE_CHANGED;
+	}
 
 #ifdef USE_STDEV
 	/*
@@ -219,7 +224,7 @@ static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 	 * clients will have different views of what "device"
 	 * the filesystem is on
 	 */
-	if (ce->ce_dev != (unsigned int) st->st_dev)
+	if (!minimal_stat && ce->ce_dev != (unsigned int) st->st_dev)
 		changed |= INODE_CHANGED;
 #endif
 
-- 
1.8.0.msysgit.0.dirty