sparse-checkout: create 'add' subcommand

When using the sparse-checkout feature, a user may want to incrementally
grow their sparse-checkout pattern set. Allow adding patterns using a
new 'add' subcommand. This is not much different from the 'set'
subcommand, because we still want to allow the '--stdin' option and
interpret inputs as directories when in cone mode and patterns
otherwise.

When in cone mode, we are growing the cone. This may actually reduce the
set of patterns when adding directory A when A/B is already a directory
in the cone. Test the different cases: siblings, parents, ancestors.

When not in cone mode, we can only assume the patterns should be
appended to the sparse-checkout file.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-sparse-checkout.txt

@@ -59,6 +59,13 @@ directories. The input format matches the output of `git ls-tree --name-only`.
 This includes interpreting pathnames that begin with a double quote (") as
 C-style quoted strings.
 
+'add'::
+	Update the sparse-checkout file to include additional patterns.
+	By default, these patterns are read from the command-line arguments,
+	but they can be read from stdin using the `--stdin` option. When
+	`core.sparseCheckoutCone` is enabled, the given patterns are interpreted
+	as directory names as in the 'set' subcommand.
+
 'disable'::
 	Disable the `core.sparseCheckout` config setting, and restore the
 	working directory to include all files. Leaves the sparse-checkout

builtin/sparse-checkout.c

@@ -18,7 +18,7 @@
 static const char *empty_base = "";
 
 static char const * const builtin_sparse_checkout_usage[] = {
-	N_("git sparse-checkout (init|list|set|disable) <options>"),
+	N_("git sparse-checkout (init|list|set|add|disable) <options>"),
 	NULL
 };
 
@@ -404,7 +404,7 @@ static void strbuf_to_cone_pattern(struct strbuf *line, struct pattern_list *pl)
 }
 
 static char const * const builtin_sparse_checkout_set_usage[] = {
-	N_("git sparse-checkout set (--stdin | <patterns>)"),
+	N_("git sparse-checkout (set|add) (--stdin | <patterns>)"),
 	NULL
 };
 
@@ -464,8 +464,54 @@ static void add_patterns_from_input(struct pattern_list *pl,
 
 enum modify_type {
 	REPLACE,
+	ADD,
 };
 
+static void add_patterns_cone_mode(int argc, const char **argv,
+				   struct pattern_list *pl)
+{
+	struct strbuf buffer = STRBUF_INIT;
+	struct pattern_entry *pe;
+	struct hashmap_iter iter;
+	struct pattern_list existing;
+	char *sparse_filename = get_sparse_checkout_filename();
+
+	add_patterns_from_input(pl, argc, argv);
+
+	memset(&existing, 0, sizeof(existing));
+	existing.use_cone_patterns = core_sparse_checkout_cone;
+
+	if (add_patterns_from_file_to_list(sparse_filename, "", 0,
+					   &existing, NULL))
+		die(_("unable to load existing sparse-checkout patterns"));
+	free(sparse_filename);
+
+	hashmap_for_each_entry(&existing.recursive_hashmap, &iter, pe, ent) {
+		if (!hashmap_contains_parent(&pl->recursive_hashmap,
+					pe->pattern, &buffer) ||
+		    !hashmap_contains_parent(&pl->parent_hashmap,
+					pe->pattern, &buffer)) {
+			strbuf_reset(&buffer);
+			strbuf_addstr(&buffer, pe->pattern);
+			insert_recursive_pattern(pl, &buffer);
+		}
+	}
+
+	clear_pattern_list(&existing);
+	strbuf_release(&buffer);
+}
+
+static void add_patterns_literal(int argc, const char **argv,
+				 struct pattern_list *pl)
+{
+	char *sparse_filename = get_sparse_checkout_filename();
+	if (add_patterns_from_file_to_list(sparse_filename, "", 0,
+					   pl, NULL))
+		die(_("unable to load existing sparse-checkout patterns"));
+	free(sparse_filename);
+	add_patterns_from_input(pl, argc, argv);
+}
+
 static int modify_pattern_list(int argc, const char **argv, enum modify_type m)
 {
 	int result;
@@ -473,7 +519,18 @@ static int modify_pattern_list(int argc, const char **argv, enum modify_type m)
 	struct pattern_list pl;
 	memset(&pl, 0, sizeof(pl));
 
-	add_patterns_from_input(&pl, argc, argv);
+	switch (m) {
+	case ADD:
+		if (core_sparse_checkout_cone)
+			add_patterns_cone_mode(argc, argv, &pl);
+		else
+			add_patterns_literal(argc, argv, &pl);
+		break;
+
+	case REPLACE:
+		add_patterns_from_input(&pl, argc, argv);
+		break;
+	}
 
 	if (!core_apply_sparse_checkout) {
 		set_config(MODE_ALL_PATTERNS);
@@ -490,7 +547,8 @@ static int modify_pattern_list(int argc, const char **argv, enum modify_type m)
 	return result;
 }
 
-static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
+static int sparse_checkout_set(int argc, const char **argv, const char *prefix,
+			       enum modify_type m)
 {
 	static struct option builtin_sparse_checkout_set_options[] = {
 		OPT_BOOL(0, "stdin", &set_opts.use_stdin,
@@ -507,7 +565,7 @@ static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
 			     builtin_sparse_checkout_set_usage,
 			     PARSE_OPT_KEEP_UNKNOWN);
 
-	return modify_pattern_list(argc, argv, REPLACE);
+	return modify_pattern_list(argc, argv, m);
 }
 
 static int sparse_checkout_disable(int argc, const char **argv)
@@ -558,7 +616,9 @@ int cmd_sparse_checkout(int argc, const char **argv, const char *prefix)
 		if (!strcmp(argv[0], "init"))
 			return sparse_checkout_init(argc, argv);
 		if (!strcmp(argv[0], "set"))
-			return sparse_checkout_set(argc, argv, prefix);
+			return sparse_checkout_set(argc, argv, prefix, REPLACE);
+		if (!strcmp(argv[0], "add"))
+			return sparse_checkout_set(argc, argv, prefix, ADD);
 		if (!strcmp(argv[0], "disable"))
 			return sparse_checkout_disable(argc, argv);
 	}

t/t1091-sparse-checkout-builtin.sh

@@ -141,6 +141,21 @@ test_expect_success 'set sparse-checkout using --stdin' '
 	check_files repo "a folder1 folder2"
 '
 
+test_expect_success 'add to sparse-checkout' '
+	cat repo/.git/info/sparse-checkout >expect &&
+	cat >add <<-\EOF &&
+	pattern1
+	/folder1/
+	pattern2
+	EOF
+	cat add >>expect &&
+	git -C repo sparse-checkout add --stdin <add &&
+	git -C repo sparse-checkout list >actual &&
+	test_cmp expect actual &&
+	test_cmp expect repo/.git/info/sparse-checkout &&
+	check_files repo "a folder1 folder2"
+'
+
 test_expect_success 'cone mode: match patterns' '
 	git -C repo config --worktree core.sparseCheckoutCone true &&
 	rm -rf repo/a repo/folder1 repo/folder2 &&
@@ -219,8 +234,52 @@ test_expect_success 'cone mode: set with nested folders' '
 	test_cmp repo/.git/info/sparse-checkout expect
 '
 
+test_expect_success 'cone mode: add independent path' '
+	git -C repo sparse-checkout set deep/deeper1 &&
+	git -C repo sparse-checkout add folder1 &&
+	cat >expect <<-\EOF &&
+	/*
+	!/*/
+	/deep/
+	!/deep/*/
+	/deep/deeper1/
+	/folder1/
+	EOF
+	test_cmp expect repo/.git/info/sparse-checkout &&
+	check_files repo a deep folder1
+'
+
+test_expect_success 'cone mode: add sibling path' '
+	git -C repo sparse-checkout set deep/deeper1 &&
+	git -C repo sparse-checkout add deep/deeper2 &&
+	cat >expect <<-\EOF &&
+	/*
+	!/*/
+	/deep/
+	!/deep/*/
+	/deep/deeper1/
+	/deep/deeper2/
+	EOF
+	test_cmp expect repo/.git/info/sparse-checkout &&
+	check_files repo a deep
+'
+
+test_expect_success 'cone mode: add parent path' '
+	git -C repo sparse-checkout set deep/deeper1 folder1 &&
+	git -C repo sparse-checkout add deep &&
+	cat >expect <<-\EOF &&
+	/*
+	!/*/
+	/deep/
+	/folder1/
+	EOF
+	test_cmp expect repo/.git/info/sparse-checkout &&
+	check_files repo a deep folder1
+'
+
 test_expect_success 'revert to old sparse-checkout on bad update' '
 	test_when_finished git -C repo reset --hard &&
+	git -C repo sparse-checkout set deep &&
 	echo update >repo/deep/deeper2/a &&
 	cp repo/.git/info/sparse-checkout expect &&
 	test_must_fail git -C repo sparse-checkout set deep/deeper1 2>err &&