[PATCH 1/5] Prevent diff machinery from examining worktree outside sparse checkout

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

---
 diff-lib.c |    5 +++--
 diff.c     |    4 +++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/diff-lib.c b/diff-lib.c
index b7813af..4094f18 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -159,7 +159,7 @@ int run_diff_files(struct rev_info *revs, unsigned int option)
 				continue;
 		}
 
-		if (ce_uptodate(ce))
+		if (ce_uptodate(ce) || ce->ce_flags & CE_VALID)
 			continue;
 
 		changed = check_removed(ce, &st);
@@ -337,6 +337,8 @@ static void do_oneway_diff(struct unpack_trees_options *o,
 	struct rev_info *revs = o->unpack_data;
 	int match_missing, cached;
 
+	/* if the entry is not checked out, don't examine work tree */
+	cached = o->index_only || (idx && idx->ce_flags & CE_VALID);
 	/*
 	 * Backward compatibility wart - "diff-index -m" does
 	 * not mean "do not ignore merges", but "match_missing".
@@ -344,7 +346,6 @@ static void do_oneway_diff(struct unpack_trees_options *o,
 	 * But with the revision flag parsing, that's found in
 	 * "!revs->ignore_merges".
 	 */
-	cached = o->index_only;
 	match_missing = !revs->ignore_merges;
 
 	if (cached && idx && ce_stage(idx)) {
diff --git a/diff.c b/diff.c
index 91d6ea2..de1bd87 100644
--- a/diff.c
+++ b/diff.c
@@ -1810,8 +1810,10 @@ static int reuse_worktree_file(const char *name, const unsigned char *sha1, int
 
 	/*
 	 * If ce matches the file in the work tree, we can reuse it.
+	 * For sparse checkout case, ce_uptodate() may be true although
+	 * the file may or may not exist in the work tree.
 	 */
-	if (ce_uptodate(ce) ||
+	if ((ce_uptodate(ce) && !(ce->ce_flags & CE_VALID)) ||
 	    (!lstat(name, &st) && !ce_match_stat(ce, &st, 0)))
 		return 1;
 
-- 
1.6.3.2.448.gdf8b6