read-cache: close index.lock in do_write_index

Teach do_write_index() to close the index.lock file
before getting the mtime and updating the istate.timestamp
fields.

On Windows, a file's mtime is not updated until the file is
closed.  On Linux, the mtime is set after the last flush.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

read-cache.c

@@ -2011,9 +2011,10 @@ void update_index_if_able(struct index_state *istate, struct lock_file *lockfile
 		rollback_lock_file(lockfile);
 }
 
-static int do_write_index(struct index_state *istate, int newfd,
+static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
 			  int strip_extensions)
 {
+	int newfd = tempfile->fd;
 	git_SHA_CTX c;
 	struct cache_header hdr;
 	int i, err, removed, extended, hdr_version;
@@ -2122,7 +2123,11 @@ static int do_write_index(struct index_state *istate, int newfd,
 			return -1;
 	}
 
-	if (ce_flush(&c, newfd, istate->sha1) || fstat(newfd, &st))
+	if (ce_flush(&c, newfd, istate->sha1))
+		return -1;
+	if (close_tempfile(tempfile))
+		return error(_("could not close '%s'"), tempfile->filename.buf);
+	if (stat(tempfile->filename.buf, &st))
 		return -1;
 	istate->timestamp.sec = (unsigned int)st.st_mtime;
 	istate->timestamp.nsec = ST_MTIME_NSEC(st);
@@ -2145,7 +2150,7 @@ static int commit_locked_index(struct lock_file *lk)
 static int do_write_locked_index(struct index_state *istate, struct lock_file *lock,
 				 unsigned flags)
 {
-	int ret = do_write_index(istate, get_lock_file_fd(lock), 0);
+	int ret = do_write_index(istate, &lock->tempfile, 0);
 	if (ret)
 		return ret;
 	assert((flags & (COMMIT_LOCK | CLOSE_LOCK)) !=
@@ -2183,7 +2188,7 @@ static int write_shared_index(struct index_state *istate,
 		return do_write_locked_index(istate, lock, flags);
 	}
 	move_cache_to_base_index(istate);
-	ret = do_write_index(si->base, fd, 1);
+	ret = do_write_index(si->base, &temporary_sharedindex, 1);
 	if (ret) {
 		delete_tempfile(&temporary_sharedindex);
 		return ret;