apply: add --intent-to-add

Similar to 'git reset -N', this option makes 'git apply' automatically
mark new files as intent-to-add so they are visible in the following
'git diff' command and could also be committed with 'git commit -a'.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-apply.txt

@@ -9,7 +9,7 @@ git-apply - Apply a patch to files and/or to the index
 SYNOPSIS
 --------
 [verse]
-'git apply' [--stat] [--numstat] [--summary] [--check] [--index] [--3way]
+'git apply' [--stat] [--numstat] [--summary] [--check] [--index | --intent-to-add] [--3way]
 	  [--apply] [--no-add] [--build-fake-ancestor=<file>] [-R | --reverse]
 	  [--allow-binary-replacement | --binary] [--reject] [-z]
 	  [-p<n>] [-C<n>] [--inaccurate-eof] [--recount] [--cached]
@@ -74,6 +74,14 @@ OPTIONS
 	cached data, apply the patch, and store the result in the index
 	without using the working tree. This implies `--index`.
 
+--intent-to-add::
+	When applying the patch only to the working tree, mark new
+	files to be added to the index later (see `--intent-to-add`
+	option in linkgit:git-add[1]). This option is ignored unless
+	running in a Git repository and `--index` is not specified.
+	Note that `--index` could be implied by other options such
+	as `--cached` or `--3way`.
+
 -3::
 --3way::
 	When the patch does not apply cleanly, fall back on 3-way merge if

apply.c

@@ -141,6 +141,8 @@ int check_apply_state(struct apply_state *state, int force_apply)
 			return error(_("--cached outside a repository"));
 		state->check_index = 1;
 	}
+	if (state->ita_only && (state->check_index || is_not_gitdir))
+		state->ita_only = 0;
 	if (state->check_index)
 		state->unsafe_paths = 0;
 
@@ -4242,7 +4244,7 @@ static void patch_stats(struct apply_state *state, struct patch *patch)
 
 static int remove_file(struct apply_state *state, struct patch *patch, int rmdir_empty)
 {
-	if (state->update_index) {
+	if (state->update_index && !state->ita_only) {
 		if (remove_file_from_cache(patch->old_name) < 0)
 			return error(_("unable to remove %s from index"), patch->old_name);
 	}
@@ -4265,15 +4267,15 @@ static int add_index_file(struct apply_state *state,
 	int namelen = strlen(path);
 	unsigned ce_size = cache_entry_size(namelen);
 
-	if (!state->update_index)
-		return 0;
-
 	ce = xcalloc(1, ce_size);
 	memcpy(ce->name, path, namelen);
 	ce->ce_mode = create_ce_mode(mode);
 	ce->ce_flags = create_ce_flags(0);
 	ce->ce_namelen = namelen;
-	if (S_ISGITLINK(mode)) {
+	if (state->ita_only) {
+		ce->ce_flags |= CE_INTENT_TO_ADD;
+		set_object_name_for_intent_to_add_entry(ce);
+	} else if (S_ISGITLINK(mode)) {
 		const char *s;
 
 		if (!skip_prefix(buf, "Subproject commit ", &s) ||
@@ -4465,8 +4467,9 @@ static int create_file(struct apply_state *state, struct patch *patch)
 
 	if (patch->conflicted_threeway)
 		return add_conflicted_stages_file(state, patch);
-	else
+	else if (state->update_index)
 		return add_index_file(state, path, mode, buf, size);
+	return 0;
 }
 
 /* phase zero is to remove, phase one is to create */
@@ -4686,7 +4689,7 @@ static int apply_patch(struct apply_state *state,
 	if (state->whitespace_error && (state->ws_error_action == die_on_ws_error))
 		state->apply = 0;
 
-	state->update_index = state->check_index && state->apply;
+	state->update_index = (state->check_index || state->ita_only) && state->apply;
 	if (state->update_index && !is_lock_file_locked(&state->lock_file)) {
 		if (state->index_file)
 			hold_lock_file_for_update(&state->lock_file,
@@ -4941,6 +4944,8 @@ int apply_parse_options(int argc, const char **argv,
 			N_("instead of applying the patch, see if the patch is applicable")),
 		OPT_BOOL(0, "index", &state->check_index,
 			N_("make sure the patch is applicable to the current index")),
+		OPT_BOOL('N', "intent-to-add", &state->ita_only,
+			N_("mark new files with `git add --intent-to-add`")),
 		OPT_BOOL(0, "cached", &state->cached,
 			N_("apply a patch without touching the working tree")),
 		OPT_BOOL_F(0, "unsafe-paths", &state->unsafe_paths,

apply.h

@@ -45,6 +45,7 @@ struct apply_state {
 	int check; /* preimage must match working tree, don't actually apply */
 	int check_index; /* preimage must match the indexed version */
 	int update_index; /* check_index && apply */
+	int ita_only;	  /* add intent-to-add entries to the index */
 
 	/* These control cosmetic aspect of the output */
 	int diffstat; /* just show a diffstat, and don't actually apply */

t/t2203-add-intent.sh

@@ -245,6 +245,7 @@ test_expect_success 'diff-files/diff-cached shows ita as new/not-new files' '
 	test_cmp expected2 actual2
 '
 
+
 test_expect_success '"diff HEAD" includes ita as new files' '
 	git reset --hard &&
 	echo new >new-ita &&
@@ -262,4 +263,16 @@ test_expect_success '"diff HEAD" includes ita as new files' '
 	test_cmp expected actual
 '
 
+test_expect_success 'apply --intent-to-add' '
+	git reset --hard &&
+	echo new >new-ita &&
+	git add -N new-ita &&
+	git diff >expected &&
+	grep "new file" expected &&
+	git reset --hard &&
+	git apply --intent-to-add expected &&
+	git diff >actual &&
+	test_cmp expected actual
+'
+
 test_done