sparse-checkout: 'set' subcommand

The 'git sparse-checkout set' subcommand takes a list of patterns
as arguments and writes them to the sparse-checkout file. Then, it
updates the working directory using 'git read-tree -mu HEAD'.

The 'set' subcommand will replace the entire contents of the
sparse-checkout file. The write_patterns_and_update() method is
extracted from cmd_sparse_checkout() to make it easier to implement
'add' and/or 'remove' subcommands in the future.

If the core.sparseCheckout config setting is disabled, then enable
the config setting in the worktree config. If we set the config
this way and the sparse-checkout fails, then re-disable the config
setting.

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

3 files changed, 84 insertions, 2 deletions

diff --git a/Documentation/git-sparse-checkout.txt b/Documentation/git-sparse-checkout.txt
index 491be1345f..ca62669b8c 100644
--- a/Documentation/git-sparse-checkout.txt
+++ b/Documentation/git-sparse-checkout.txt
@@ -42,6 +42,12 @@ To avoid interfering with other worktrees, it first enables the
 `extensions.worktreeConfig` setting and makes sure to set the
 `core.sparseCheckout` setting in the worktree-specific config file.
 
+'set'::
+	Write a set of patterns to the sparse-checkout file, as given as
+	a list of arguments following the 'set' subcommand. Update the
+	working directory to match the new patterns. Enable the
+	core.sparseCheckout config setting if it is not already enabled.
+
 SPARSE CHECKOUT
 ---------------
 
diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
index e3418fbe2a..95cbd0a42c 100644
--- a/builtin/sparse-checkout.c
+++ b/builtin/sparse-checkout.c
@@ -8,7 +8,7 @@
 #include "strbuf.h"
 
 static char const * const builtin_sparse_checkout_usage[] = {
-	N_("git sparse-checkout (init|list)"),
+	N_("git sparse-checkout (init|list|set) <options>"),
 	NULL
 };
 
@@ -66,7 +66,7 @@ static int update_working_directory(void)
 	argv_array_pushl(&argv, "read-tree", "-m", "-u", "HEAD", NULL);
 
 	if (run_command_v_opt(argv.argv, RUN_GIT_CMD)) {
-		error(_("failed to update index with new sparse-checkout paths"));
+		error(_("failed to update index with new sparse-checkout patterns"));
 		result = 1;
 	}
 
@@ -136,6 +136,47 @@ reset_dir:
 	return update_working_directory();
 }
 
+static int write_patterns_and_update(struct pattern_list *pl)
+{
+	char *sparse_filename;
+	FILE *fp;
+
+	sparse_filename = get_sparse_checkout_filename();
+	fp = fopen(sparse_filename, "w");
+	write_patterns_to_file(fp, pl);
+	fclose(fp);
+	free(sparse_filename);
+
+	return update_working_directory();
+}
+
+static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
+{
+	static const char *empty_base = "";
+	int i;
+	struct pattern_list pl;
+	int result;
+	int changed_config = 0;
+	memset(&pl, 0, sizeof(pl));
+
+	for (i = 1; i < argc; i++)
+		add_pattern(argv[i], empty_base, 0, &pl, 0);
+
+	if (!core_apply_sparse_checkout) {
+		set_config(MODE_ALL_PATTERNS);
+		core_apply_sparse_checkout = 1;
+		changed_config = 1;
+	}
+
+	result = write_patterns_and_update(&pl);
+
+	if (result && changed_config)
+		set_config(MODE_NO_PATTERNS);
+
+	clear_pattern_list(&pl);
+	return result;
+}
+
 int cmd_sparse_checkout(int argc, const char **argv, const char *prefix)
 {
 	static struct option builtin_sparse_checkout_options[] = {
@@ -158,6 +199,8 @@ int cmd_sparse_checkout(int argc, const char **argv, const char *prefix)
 			return sparse_checkout_list(argc, argv);
 		if (!strcmp(argv[0], "init"))
 			return sparse_checkout_init(argc, argv);
+		if (!strcmp(argv[0], "set"))
+			return sparse_checkout_set(argc, argv, prefix);
 	}
 
 	usage_with_options(builtin_sparse_checkout_usage,
diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
index 78c20cb7e3..72d8bc5c25 100755
--- a/t/t1091-sparse-checkout-builtin.sh
+++ b/t/t1091-sparse-checkout-builtin.sh
@@ -95,4 +95,37 @@ test_expect_success 'clone --sparse' '
 	test_cmp expect dir
 '
 
+test_expect_success 'set enables config' '
+	git init empty-config &&
+	(
+		cd empty-config &&
+		test_commit test file &&
+		test_path_is_missing .git/config.worktree &&
+		test_must_fail git sparse-checkout set nothing &&
+		test_path_is_file .git/config.worktree &&
+		test_must_fail git config core.sparseCheckout &&
+		git sparse-checkout set "/*" &&
+		test_cmp_config true core.sparseCheckout
+	)
+'
+
+test_expect_success 'set sparse-checkout using builtin' '
+	git -C repo sparse-checkout set "/*" "!/*/" "*folder*" &&
+	cat >expect <<-EOF &&
+		/*
+		!/*/
+		*folder*
+	EOF
+	git -C repo sparse-checkout list >actual &&
+	test_cmp expect actual &&
+	test_cmp expect repo/.git/info/sparse-checkout &&
+	ls repo >dir  &&
+	cat >expect <<-EOF &&
+		a
+		folder1
+		folder2
+	EOF
+	test_cmp expect dir
+'
+
 test_done