apply tests: GIT_APPLY_LOCATION_INDEX with generated patches

Test a simple patch application with `GIT_APPLY_LOCATION_INDEX`, which
emulates `git apply --cached`.

tests/apply/apply_helpers.h

@@ -152,3 +152,30 @@ static void validate_index_unchanged(git_repository *repo)
 	git_tree_free(head);
 	git_index_free(index);
 }
+
+static void validate_workdir_unchanged(git_repository *repo)
+{
+	git_tree *head;
+	git_index *index;
+	git_iterator *head_iterator, *workdir_iterator, *iterators[2];
+	git_iterator_options workdir_opts = GIT_ITERATOR_OPTIONS_INIT;
+
+	cl_git_pass(git_repository_head_tree(&head, repo));
+	cl_git_pass(git_repository_index(&index, repo));
+
+	workdir_opts.flags |= GIT_ITERATOR_INCLUDE_HASH;
+
+	cl_git_pass(git_iterator_for_tree(&head_iterator, head, NULL));
+	cl_git_pass(git_iterator_for_workdir(&workdir_iterator, repo, index, NULL, &workdir_opts));
+
+	iterators[0] = head_iterator;
+	iterators[1] = workdir_iterator;
+
+	cl_git_pass(git_iterator_walk(iterators, 2, iterator_eq, NULL));
+
+	git_iterator_free(head_iterator);
+	git_iterator_free(workdir_iterator);
+
+	git_tree_free(head);
+	git_index_free(index);
+}

tests/apply/index.c

+#include "clar_libgit2.h"
+#include "apply_helpers.h"
+
+static git_repository *repo;
+
+#define TEST_REPO_PATH "merge-recursive"
+
+void test_apply_index__initialize(void)
+{
+	git_oid oid;
+	git_commit *commit;
+
+	repo = cl_git_sandbox_init(TEST_REPO_PATH);
+
+	git_oid_fromstr(&oid, "539bd011c4822c560c1d17cab095006b7a10f707");
+	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
+	cl_git_pass(git_reset(repo, (git_object *)commit, GIT_RESET_HARD, NULL));
+	git_commit_free(commit);
+}
+
+void test_apply_index__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+}
+
+void test_apply_index__generate_diff(void)
+{
+	git_oid a_oid, b_oid;
+	git_commit *a_commit, *b_commit;
+	git_tree *a_tree, *b_tree;
+	git_diff *diff;
+	git_diff_options diff_opts = GIT_DIFF_OPTIONS_INIT;
+	git_apply_options opts = GIT_APPLY_OPTIONS_INIT;
+
+	struct merge_index_entry index_expected[] = {
+		{ 0100644, "ffb36e513f5fdf8a6ba850a20142676a2ac4807d", 0, "asparagus.txt" },
+		{ 0100644, "68f6182f4c85d39e1309d97c7e456156dc9c0096", 0, "beef.txt" },
+		{ 0100644, "4b7c5650008b2e747fe1809eeb5a1dde0e80850a", 0, "bouilli.txt" },
+		{ 0100644, "c4e6cca3ec6ae0148ed231f97257df8c311e015f", 0, "gravy.txt" },
+		{ 0100644, "68af1fc7407fd9addf1701a87eb1c95c7494c598", 0, "oyster.txt" },
+		{ 0100644, "a7b066537e6be7109abfe4ff97b675d4e077da20", 0, "veal.txt" },
+	};
+	size_t index_expected_cnt = sizeof(index_expected) /
+		sizeof(struct merge_index_entry);
+
+	git_oid_fromstr(&a_oid, "539bd011c4822c560c1d17cab095006b7a10f707");
+	git_oid_fromstr(&b_oid, "7c7bf85e978f1d18c0566f702d2cb7766b9c8d4f");
+	cl_git_pass(git_commit_lookup(&a_commit, repo, &a_oid));
+	cl_git_pass(git_commit_lookup(&b_commit, repo, &b_oid));
+
+	cl_git_pass(git_commit_tree(&a_tree, a_commit));
+	cl_git_pass(git_commit_tree(&b_tree, b_commit));
+
+	cl_git_pass(git_diff_tree_to_tree(&diff, repo, a_tree, b_tree, &diff_opts));
+
+	opts.location = GIT_APPLY_LOCATION_INDEX;
+	cl_git_pass(git_apply(repo, diff, &opts));
+
+	validate_apply_index(repo, index_expected, index_expected_cnt);
+	validate_workdir_unchanged(repo);
+
+	git_diff_free(diff);
+	git_tree_free(a_tree);
+	git_tree_free(b_tree);
+	git_commit_free(a_commit);
+	git_commit_free(b_commit);
+}