Merge branch 'tn/stash-avoid-sparse-index-expansion' into jch

The 'git stash push' command has been optimized to avoid unnecessary
sparse index expansion when pathspecs are wholly inside the
sparse-checkout cone.  Also, a potential out-of-bounds read in the
sparse-index expansion check helper pathspec_needs_expanded_index()
has been fixed by consistently using the parsed, prefixed path.

* tn/stash-avoid-sparse-index-expansion:
  stash: avoid sparse-index expansion for in-cone paths
  pathspec: use match for sparse-index expansion checks

builtin/stash.c

@@ -1702,8 +1702,8 @@ static int do_push_stash(const struct pathspec *ps, const char *stash_msg, int q
 	if (!include_untracked && ps->nr) {
 		char *ps_matched = xcalloc(ps->nr, 1);
 
-		/* TODO: audit for interaction with sparse-index. */
-		ensure_full_index(the_repository->index);
+		if (pathspec_needs_expanded_index(the_repository->index, ps))
+			ensure_full_index(the_repository->index);
 		for (size_t i = 0; i < the_repository->index->cache_nr; i++)
 			ce_path_match(the_repository->index, the_repository->index->cache[i], ps,
 				      ps_matched);

pathspec.c

@@ -847,9 +847,9 @@ int pathspec_needs_expanded_index(struct index_state *istate,
 			 * - not-in-cone/bar*: may need expanded index
 			 * - **.c: may need expanded index
 			 */
-			if (strspn(item.original + item.nowildcard_len, "*") ==
+			if (strspn(item.match + item.nowildcard_len, "*") ==
 				    (unsigned int)(item.len - item.nowildcard_len) &&
-			    path_in_cone_mode_sparse_checkout(item.original, istate))
+			    path_in_cone_mode_sparse_checkout(item.match, istate))
 				continue;
 
 			for (pos = 0; pos < istate->cache_nr; pos++) {
@@ -865,7 +865,7 @@ int pathspec_needs_expanded_index(struct index_state *istate,
 				 */
 				if ((unsigned int)item.nowildcard_len >
 					    ce_namelen(ce) &&
-				    !strncmp(item.original, ce->name,
+				    !strncmp(item.match, ce->name,
 					     ce_namelen(ce))) {
 					res = 1;
 					break;
@@ -876,13 +876,13 @@ int pathspec_needs_expanded_index(struct index_state *istate,
 				 * directory and the pathspec does not match the whole
 				 * directory, need to expand the index.
 				 */
-				if (!strncmp(item.original, ce->name, item.nowildcard_len) &&
-				    wildmatch(item.original, ce->name, 0)) {
+				if (!strncmp(item.match, ce->name, item.nowildcard_len) &&
+				    wildmatch(item.match, ce->name, 0)) {
 					res = 1;
 					break;
 				}
 			}
-		} else if (!path_in_cone_mode_sparse_checkout(item.original, istate) &&
+		} else if (!path_in_cone_mode_sparse_checkout(item.match, istate) &&
 			   !matches_skip_worktree(pathspec, i, &skip_worktree_seen))
 			res = 1;
 

t/perf/p2000-sparse-operations.sh

@@ -108,6 +108,7 @@ test_perf_on_all () {
 
 test_perf_on_all git status
 test_perf_on_all 'git stash && git stash pop'
+test_perf_on_all "git stash push -- $SPARSE_CONE/a && git stash pop"
 test_perf_on_all 'echo >>new && git stash -u && git stash pop'
 test_perf_on_all git add -A
 test_perf_on_all git add .

t/t1092-sparse-checkout-compatibility.sh

@@ -1598,6 +1598,61 @@ test_expect_success 'sparse-index is not expanded: stash' '
 	ensure_not_expanded stash pop
 '
 
+test_expect_success 'sparse-index is not expanded: stash in-cone pathspec' '
+	init_repos &&
+
+	echo unrelated >>sparse-index/deep/e &&
+	echo literal >>sparse-index/deep/a &&
+	ensure_not_expanded stash push -- deep/a &&
+	test_grep ! literal sparse-index/deep/a &&
+	test_grep unrelated sparse-index/deep/e &&
+	ensure_not_expanded stash pop &&
+	test_grep literal sparse-index/deep/a &&
+
+	echo prefixed >>sparse-index/deep/a &&
+	ensure_not_expanded -C deep stash push -- a &&
+	test_grep ! prefixed sparse-index/deep/a &&
+	test_grep unrelated sparse-index/deep/e &&
+	ensure_not_expanded stash pop &&
+	test_grep prefixed sparse-index/deep/a &&
+
+	echo wildcard >>sparse-index/deep/a &&
+	ensure_not_expanded stash push -- "deep/a*" &&
+	test_grep ! wildcard sparse-index/deep/a &&
+	test_grep unrelated sparse-index/deep/e &&
+	ensure_not_expanded stash pop &&
+	test_grep wildcard sparse-index/deep/a &&
+
+	echo pathspec-file >>sparse-index/deep/a &&
+	echo deep/a >pathspec-file &&
+	ensure_not_expanded stash push --pathspec-from-file=../pathspec-file &&
+	test_grep ! pathspec-file sparse-index/deep/a &&
+	test_grep unrelated sparse-index/deep/e &&
+	ensure_not_expanded stash pop &&
+	test_grep pathspec-file sparse-index/deep/a &&
+
+	echo multiple-a >>sparse-index/deep/a &&
+	echo multiple-e >>sparse-index/deep/e &&
+	ensure_not_expanded stash push -- deep/a deep/e &&
+	test_grep ! multiple-a sparse-index/deep/a &&
+	test_grep ! multiple-e sparse-index/deep/e &&
+	ensure_not_expanded stash pop &&
+	test_grep multiple-a sparse-index/deep/a &&
+	test_grep multiple-e sparse-index/deep/e &&
+
+	echo staged >>sparse-index/deep/a &&
+	git -C sparse-index add deep/a &&
+	ensure_not_expanded stash push --staged -- deep/a &&
+	test_grep ! staged sparse-index/deep/a &&
+	test_grep unrelated sparse-index/deep/e &&
+	ensure_not_expanded stash pop --index &&
+	test_grep staged sparse-index/deep/a &&
+	test_must_fail git -C sparse-index diff --cached --quiet -- deep/a &&
+
+	ensure_not_expanded ! stash push -- deep/does-not-exist &&
+	test_grep "did not match any file" sparse-index-error
+'
+
 test_expect_success 'describe tested on all' '
 	init_repos &&
 
@@ -2119,6 +2174,13 @@ test_expect_success 'sparse index is not expanded: rm' '
 	ensure_not_expanded rm -r deep
 '
 
+test_expect_success 'sparse index is not expanded: prefixed wildcard pathspec' '
+	init_repos &&
+
+	ensure_not_expanded -C deep rm --dry-run -- "a*" &&
+	ensure_not_expanded -C deep reset base -- "a*"
+'
+
 test_expect_success 'grep with and --cached' '
 	init_repos &&