[PATCH 4/9] sparse-checkout: 'add' subcommand

["Derrick Stolee via GitGitGadget" <gitgitgadget@xxxxxxxxx>]

From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>

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

Note: if a user adds a negative pattern that would lead to the
removal of a non-empty directory, then Git may not delete that
directory (on Windows).

Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
---
 Documentation/git-sparse-checkout.txt |  4 ++++
 builtin/sparse-checkout.c             | 32 ++++++++++++++++++++++++++-
 t/t1091-sparse-checkout-builtin.sh    | 20 +++++++++++++++++
 3 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-sparse-checkout.txt b/Documentation/git-sparse-checkout.txt
index 50c53ee60a..6f540a3443 100644
--- a/Documentation/git-sparse-checkout.txt
+++ b/Documentation/git-sparse-checkout.txt
@@ -34,6 +34,10 @@ COMMANDS
 	by Git. Add patterns to the sparse-checkout file to
 	repopulate the working directory.
 
+'add'::
+	Add a set of patterns to the sparse-checkout file, as given over
+	stdin. Updates the working directory to match the new patterns.
+
 SPARSE CHECKOUT
 ----------------
 
diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
index 86d24e6295..ec6134fecc 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|add|list]"),
 	NULL
 };
 
@@ -166,6 +166,34 @@ static int sparse_checkout_init(int argc, const char **argv)
 	return sc_read_tree();
 }
 
+static int sparse_checkout_add(int argc, const char **argv)
+{
+	struct exclude_list el;
+	char *sparse_filename;
+	FILE *fp;
+	struct strbuf line = STRBUF_INIT;
+
+	memset(&el, 0, sizeof(el));
+
+	sparse_filename = get_sparse_checkout_filename();
+	add_excludes_from_file_to_list(sparse_filename, "", 0, &el, NULL);
+
+	fp = fopen(sparse_filename, "w");
+	write_excludes_to_file(fp, &el);
+
+	while (!strbuf_getline(&line, stdin)) {
+		strbuf_trim(&line);
+		fprintf(fp, "%s\n", line.buf);
+	}
+
+	fclose(fp);
+	free(sparse_filename);
+
+	clear_exclude_list(&el);
+
+	return sc_read_tree();
+}
+
 int cmd_sparse_checkout(int argc, const char **argv, const char *prefix)
 {
 	static struct option builtin_sparse_checkout_options[] = {
@@ -187,6 +215,8 @@ 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], "add"))
+			return sparse_checkout_add(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 b7d5f15830..499bd8d6d0 100755
--- a/t/t1091-sparse-checkout-builtin.sh
+++ b/t/t1091-sparse-checkout-builtin.sh
@@ -100,4 +100,24 @@ test_expect_success 'clone --sparse' '
 	test_cmp expect dir
 '
 
+test_expect_success 'add to existing sparse-checkout' '
+	echo "/folder2/*" | git -C repo sparse-checkout add &&
+	cat >expect <<-EOF &&
+		/*
+		!/*/*
+		/folder1/*
+		/folder2/*
+	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
\ No newline at end of file
-- 
gitgitgadget