Merge branch 'rp/apply-cached-with-i-t-a'

Recent versions of "git diff-files" shows a diff between the index
and the working tree for "intent-to-add" paths as a "new file"
patch; "git apply --cached" should be able to take "git diff-files"
and should act as an equivalent to "git add" for the path, but the
command failed to do so for such a path.

* rp/apply-cached-with-i-t-a:
  t4140: test apply with i-t-a paths
  apply: make i-t-a entries never match worktree
  apply: allow "new file" patches on i-t-a entries

apply.c

@@ -3740,6 +3740,7 @@ static int check_preimage(struct apply_state *state,
 
 #define EXISTS_IN_INDEX 1
 #define EXISTS_IN_WORKTREE 2
+#define EXISTS_IN_INDEX_AS_ITA 3
 
 static int check_to_create(struct apply_state *state,
 			   const char *new_name,
@@ -3747,10 +3748,23 @@ static int check_to_create(struct apply_state *state,
 {
 	struct stat nst;
 
-	if (state->check_index &&
-	    index_name_pos(state->repo->index, new_name, strlen(new_name)) >= 0 &&
-	    !ok_if_exists)
-		return EXISTS_IN_INDEX;
+	if (state->check_index && (!ok_if_exists || !state->cached)) {
+		int pos;
+
+		pos = index_name_pos(state->repo->index, new_name, strlen(new_name));
+		if (pos >= 0) {
+			struct cache_entry *ce = state->repo->index->cache[pos];
+
+			/* allow ITA, as they do not yet exist in the index */
+			if (!ok_if_exists && !(ce->ce_flags & CE_INTENT_TO_ADD))
+				return EXISTS_IN_INDEX;
+
+			/* ITA entries can never match working tree files */
+			if (!state->cached && (ce->ce_flags & CE_INTENT_TO_ADD))
+				return EXISTS_IN_INDEX_AS_ITA;
+		}
+	}
+
 	if (state->cached)
 		return 0;
 
@@ -3935,6 +3949,9 @@ static int check_patch(struct apply_state *state, struct patch *patch)
 		case EXISTS_IN_INDEX:
 			return error(_("%s: already exists in index"), new_name);
 			break;
+		case EXISTS_IN_INDEX_AS_ITA:
+			return error(_("%s: does not match index"), new_name);
+			break;
 		case EXISTS_IN_WORKTREE:
 			return error(_("%s: already exists in working directory"),
 				     new_name);

t/t4140-apply-ita.sh

@@ -0,0 +1,56 @@
+#!/bin/sh
+
+test_description='git apply of i-t-a file'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_write_lines 1 2 3 4 5 >blueprint &&
+
+	cat blueprint >test-file &&
+	git add -N test-file &&
+	git diff >creation-patch &&
+	grep "new file mode 100644" creation-patch &&
+
+	rm -f test-file &&
+	git diff >deletion-patch &&
+	grep "deleted file mode 100644" deletion-patch
+'
+
+test_expect_success 'apply creation patch to ita path (--cached)' '
+	git rm -f test-file &&
+	cat blueprint >test-file &&
+	git add -N test-file &&
+
+	git apply --cached creation-patch &&
+	git cat-file blob :test-file >actual &&
+	test_cmp blueprint actual
+'
+
+test_expect_success 'apply creation patch to ita path (--index)' '
+	git rm -f test-file &&
+	cat blueprint >test-file &&
+	git add -N test-file &&
+	rm -f test-file &&
+
+	test_must_fail git apply --index creation-patch
+'
+
+test_expect_success 'apply deletion patch to ita path (--cached)' '
+	git rm -f test-file &&
+	cat blueprint >test-file &&
+	git add -N test-file &&
+
+	git apply --cached deletion-patch &&
+	test_must_fail git ls-files --stage --error-unmatch test-file
+'
+
+test_expect_success 'apply deletion patch to ita path (--index)' '
+	cat blueprint >test-file &&
+	git add -N test-file &&
+
+	test_must_fail git apply --index deletion-patch &&
+	git ls-files --stage --error-unmatch test-file
+'
+
+test_done