Subject: [PATCH 2/9] sparse-checkout: create 'init' subcommand

From: "Derrick Stolee via GitGitGadget" <[email-masked]>
Date: Tue, 20 Aug 2019 08:11:07 -0700 (PDT)

From: Derrick Stolee <[email-masked]>

Getting started with a sparse-checkout file can be daunting. Help
users start their sparse enlistment using 'git sparse-checkout init'.
This will set 'core.sparseCheckout=true' in their config, write
an initial set of patterns to the sparse-checkout file, and update
their working directory.

Using 'git read-tree' to clear directories does not work cleanly
on Windows, so manually delete directories that are tracked by Git
before running read-tree.

The use of running another process for 'git read-tree' is likely
suboptimal, but that can be improved in a later change, if valuable.

Signed-off-by: Derrick Stolee <[email-masked]>
---
 Documentation/git-sparse-checkout.txt |   7 ++
 builtin/sparse-checkout.c             | 106 +++++++++++++++++++++++++-
 t/t1091-sparse-checkout-builtin.sh    |  40 ++++++++++
 3 files changed, 152 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-sparse-checkout.txt b/Documentation/git-sparse-checkout.txt
index ca0ca6a12f..50c53ee60a 100644
--- a/Documentation/git-sparse-checkout.txt
+++ b/Documentation/git-sparse-checkout.txt
@@ -26,6 +26,13 @@ COMMANDS
 'list'::
 	Provide a list of the contents in the sparse-checkout file.
 
+'init'::
+	Enable the `core.sparseCheckout` setting. If the
+	sparse-checkout file does not exist, then populate it with
+	patterns that match every file in the root directory and
+	no other directories, then will remove all directories tracked
+	by Git. Add patterns to the sparse-checkout file to
+	repopulate the working directory.
 
 SPARSE CHECKOUT
 ----------------
diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
index 6477a6ed9c..86d24e6295 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 [list]"),
+	N_("git sparse-checkout [init|list]"),
 	NULL
 };
 
@@ -64,6 +64,108 @@ static int sparse_checkout_list(int argc, const char **argv)
 	return 0;
 }
 
+static int sc_read_tree(void)
+{
+	struct argv_array argv = ARGV_ARRAY_INIT;
+	int result = 0;
+	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"));
+		result = 1;
+	}
+
+	argv_array_clear(&argv);
+	return result;
+}
+
+static int sc_enable_config(void)
+{
+	struct argv_array argv = ARGV_ARRAY_INIT;
+	int result = 0;
+	argv_array_pushl(&argv, "config", "--add", "core.sparseCheckout", "true", NULL);
+
+	if (run_command_v_opt(argv.argv, RUN_GIT_CMD)) {
+		error(_("failed to enable core.sparseCheckout"));
+		result = 1;
+	}
+
+	argv_array_clear(&argv);
+	return result;
+}
+
+static int delete_directory(const struct object_id *oid, struct strbuf *base,
+		const char *pathname, unsigned mode, int stage, void *context)
+{
+	struct strbuf dirname = STRBUF_INIT;
+	struct stat sb;
+
+	strbuf_addstr(&dirname, the_repository->worktree);
+	strbuf_addch(&dirname, '/');
+	strbuf_addstr(&dirname, pathname);
+
+	if (stat(dirname.buf, &sb) || !(sb.st_mode & S_IFDIR))
+		return 0;
+
+	if (remove_dir_recursively(&dirname, 0))
+		warning(_("failed to remove directory '%s'"),
+			dirname.buf);
+
+	strbuf_release(&dirname);
+	return 0;
+}
+
+static int sparse_checkout_init(int argc, const char **argv)
+{
+	struct tree *t;
+	struct object_id oid;
+	struct exclude_list el;
+	static struct pathspec pathspec;
+	char *sparse_filename;
+	FILE *fp;
+	int res;
+
+	if (sc_enable_config())
+		return 1;
+
+	memset(&el, 0, sizeof(el));
+
+	sparse_filename = get_sparse_checkout_filename();
+	res = add_excludes_from_file_to_list(sparse_filename, "", 0, &el, NULL);
+
+	/* If we already have a sparse-checkout file, use it. */
+	if (res >= 0) {
+		free(sparse_filename);
+		goto reset_dir;
+	}
+
+	/* initial mode: all blobs at root */
+	fp = fopen(sparse_filename, "w");
+	free(sparse_filename);
+	fprintf(fp, "/*\n!/*/*\n");
+	fclose(fp);
+
+	/* remove all directories in the root, if tracked by Git */
+	if (get_oid("HEAD", &oid)) {
+		/* assume we are in a fresh repo */
+		return 0;
+	}
+
+	t = parse_tree_indirect(&oid);
+
+	parse_pathspec(&pathspec, PATHSPEC_ALL_MAGIC &
+				  ~(PATHSPEC_FROMTOP | PATHSPEC_LITERAL),
+		       PATHSPEC_PREFER_CWD,
+		       "", NULL);
+
+	if (read_tree_recursive(the_repository, t, "", 0, 0, &pathspec,
+				delete_directory, NULL))
+		return 1;
+
+reset_dir:
+	return sc_read_tree();
+}
+
 int cmd_sparse_checkout(int argc, const char **argv, const char *prefix)
 {
 	static struct option builtin_sparse_checkout_options[] = {
@@ -83,6 +185,8 @@ int cmd_sparse_checkout(int argc, const char **argv, const char *prefix)
 	if (argc > 0) {
 		if (!strcmp(argv[0], "list"))
 			return sparse_checkout_list(argc, argv);
+		if (!strcmp(argv[0], "init"))
+			return sparse_checkout_init(argc, argv);
 	}
 
 	usage_with_options(builtin_sparse_checkout_usage,
diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
index ba6928c641..35ab84aabd 100755
--- a/t/t1091-sparse-checkout-builtin.sh
+++ b/t/t1091-sparse-checkout-builtin.sh
@@ -47,4 +47,44 @@ test_expect_success 'git sparse-checkout list (populated)' '
 	test_cmp expect list
 '
 
+test_expect_success 'git sparse-checkout init' '
+	git -C repo sparse-checkout init &&
+	cat >expect <<-EOF &&
+		/*
+		!/*/*
+	EOF
+	test_cmp expect repo/.git/info/sparse-checkout &&
+	git -C repo config --list >config &&
+	test_i18ngrep "core.sparsecheckout=true" config &&
+	ls repo >dir  &&
+	echo a >expect &&
+	test_cmp expect dir
+'
+
+test_expect_success 'git sparse-checkout list after init' '
+	git -C repo sparse-checkout list >actual &&
+	cat >expect <<-EOF &&
+		/*
+		!/*/*
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'init with existing sparse-checkout' '
+	echo "/folder1/*" >> repo/.git/info/sparse-checkout &&
+	git -C repo sparse-checkout init &&
+	cat >expect <<-EOF &&
+		/*
+		!/*/*
+		/folder1/*
+	EOF
+	test_cmp expect repo/.git/info/sparse-checkout &&
+	ls repo >dir  &&
+	cat >expect <<-EOF &&
+		a
+		folder1
+	EOF
+	test_cmp expect dir
+'
+
 test_done
\ No newline at end of file
-- 
gitgitgadget