From ccdc4ec3044bd108ae1e20d772f078c10df114b3 Mon Sep 17 00:00:00 2001
From: Junio C Hamano <gitster@pobox.com>
Date: Mon, 21 Mar 2011 10:16:10 -0700
Subject: diff/status: refactor opportunistic index update

When we had to refresh the index internally before running diff or status,
we opportunistically updated the $GIT_INDEX_FILE so that later invocation
of git can use the lstat(2) we already did in this invocation.

Make them share a helper function to do so.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/commit.c b/builtin/commit.c
index 66fdd22..0b6ce2f 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1090,13 +1090,8 @@ int cmd_status(int argc, const char **argv, const char *prefix)
 	refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, s.pathspec, NULL, NULL);
 
 	fd = hold_locked_index(&index_lock, 0);
-	if (0 <= fd) {
-		if (active_cache_changed &&
-		    !write_cache(fd, active_cache, active_nr))
-			commit_locked_index(&index_lock);
-		else
-			rollback_lock_file(&index_lock);
-	}
+	if (0 <= fd)
+		update_index_if_able(&the_index, &index_lock);
 
 	s.is_initial = get_sha1(s.reference, sha1) ? 1 : 0;
 	s.in_merge = in_merge;
diff --git a/builtin/diff.c b/builtin/diff.c
index a43d326..bab4bd9 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -197,12 +197,7 @@ static void refresh_index_quietly(void)
 	discard_cache();
 	read_cache();
 	refresh_cache(REFRESH_QUIET|REFRESH_UNMERGED);
-
-	if (active_cache_changed &&
-	    !write_cache(fd, active_cache, active_nr))
-		commit_locked_index(lock_file);
-
-	rollback_lock_file(lock_file);
+	update_index_if_able(&the_index, lock_file);
 }
 
 static int builtin_diff_files(struct rev_info *revs, int argc, const char **argv)
diff --git a/cache.h b/cache.h
index 2ef2fa3..9a3cc8e 100644
--- a/cache.h
+++ b/cache.h
@@ -520,6 +520,7 @@ extern NORETURN void unable_to_lock_index_die(const char *path, int err);
 extern int hold_lock_file_for_update(struct lock_file *, const char *path, int);
 extern int hold_lock_file_for_append(struct lock_file *, const char *path, int);
 extern int commit_lock_file(struct lock_file *);
+extern void update_index_if_able(struct index_state *, struct lock_file *);
 
 extern int hold_locked_index(struct lock_file *, int);
 extern int commit_locked_index(struct lock_file *);
diff --git a/read-cache.c b/read-cache.c
index 1f42473..7a0421c 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1545,6 +1545,18 @@ static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce)
 	return result;
 }
 
+/*
+ * Opportunisticly update the index but do not complain if we can't
+ */
+void update_index_if_able(struct index_state *istate, struct lock_file *lockfile)
+{
+	if (istate->cache_changed &&
+	    !write_index(istate, lockfile->fd))
+		commit_locked_index(lockfile);
+	else
+		rollback_lock_file(lockfile);
+}
+
 int write_index(struct index_state *istate, int newfd)
 {
 	git_SHA_CTX c;
-- 
cgit v0.10.2-6-g49f6


From 483fbe2b7cb89ddcf700a677735d21aa176bc5a6 Mon Sep 17 00:00:00 2001
From: Junio C Hamano <gitster@pobox.com>
Date: Mon, 21 Mar 2011 10:18:19 -0700
Subject: update $GIT_INDEX_FILE when there are racily clean entries

Traditional "opportunistic index update" done by read-only "diff" and
"status" was about updating cached lstat(2) information in the index for
the next round.  We missed another obvious optimization opportunity: when
there are racily clean entries that will cease to be racily clean by
updating $GIT_INDEX_FILE.  Detect that case and write $GIT_INDEX_FILE out
to give it a newer timestamp.

Noticed by Lasse Makholm by stracing "git status" in a fresh checkout and
counting the number of open(2) calls.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/read-cache.c b/read-cache.c
index 7a0421c..971e277 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1545,12 +1545,25 @@ static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce)
 	return result;
 }
 
+static int has_racy_timestamp(struct index_state *istate)
+{
+	int entries = istate->cache_nr;
+	int i;
+
+	for (i = 0; i < entries; i++) {
+		struct cache_entry *ce = istate->cache[i];
+		if (is_racy_timestamp(istate, ce))
+			return 1;
+	}
+	return 0;
+}
+
 /*
  * Opportunisticly update the index but do not complain if we can't
  */
 void update_index_if_able(struct index_state *istate, struct lock_file *lockfile)
 {
-	if (istate->cache_changed &&
+	if ((istate->cache_changed || has_racy_timestamp(istate)) &&
 	    !write_index(istate, lockfile->fd))
 		commit_locked_index(lockfile);
 	else
-- 
cgit v0.10.2-6-g49f6