apply: handle file deletions

If the file was deleted in the postimage, do not attempt to update the
target.  Instead, ignore it and simply allow it to stay removed in our
computed postimage.  Also, test that we can handle file deletions.

src/apply.c

@@ -404,6 +404,9 @@ static int apply_one(
 
 	delta = git_patch_get_delta(patch);
 
+	if (delta->status == GIT_DELTA_DELETED)
+		goto done;
+
 	if ((error = git_reader_read(&pre_contents,
 			preimage_reader, delta->old_file.path)) < 0 ||
 		(error = git_apply__patch(&post_contents, &filename, &mode,

tests/apply/workdir.c

@@ -34,6 +34,9 @@ static int iterator_compare(const git_index_entry **entries, void *_data)
 	cl_assert_equal_i(head_entry->mode, index_entry->mode);
 	cl_assert_equal_s(head_entry->path, index_entry->path);
 
+	if (!workdir_entry)
+		return 0;
+
 	cl_assert_equal_i(GIT_IDXENTRY_STAGE(workdir_entry), data->expected[data->idx].stage);
 	cl_git_pass(git_oid_fromstr(&expected_id, data->expected[data->idx].oid_str));
 	cl_assert_equal_oid(&workdir_entry->id, &expected_id);
@@ -44,6 +47,7 @@ static int iterator_compare(const git_index_entry **entries, void *_data)
 		return -1;
 
 	data->idx++;
+
 	return 0;
 }
 
@@ -171,3 +175,48 @@ void test_apply_workdir__parsed_diff(void)
 	git_diff_free(diff);
 	git_commit_free(commit);
 }
+
+void test_apply_workdir__removes_file(void)
+{
+	git_oid oid;
+	git_commit *commit;
+	git_diff *diff;
+
+	const char *diff_file =
+		"diff --git a/gravy.txt b/gravy.txt\n"
+		"deleted file mode 100644\n"
+		"index c4e6cca..0000000\n"
+		"--- a/gravy.txt\n"
+		"+++ /dev/null\n"
+		"@@ -1,8 +0,0 @@\n"
+		"-GRAVY SOUP.\n"
+		"-\n"
+		"-Get eight pounds of coarse lean beef--wash it clean and lay it in your\n"
+		"-pot, put in the same ingredients as for the shin soup, with the same\n"
+		"-quantity of water, and follow the process directed for that. Strain the\n"
+		"-soup through a sieve, and serve it up clear, with nothing more than\n"
+		"-toasted bread in it; two table-spoonsful of mushroom catsup will add a\n"
+		"-fine flavour to the soup.\n";
+
+	struct merge_index_entry expected[] = {
+		{ 0100644, "f51658077d85f2264fa179b4d0848268cb3475c3", 0, "asparagus.txt" },
+		{ 0100644, "68f6182f4c85d39e1309d97c7e456156dc9c0096", 0, "beef.txt" },
+		{ 0100644, "4b7c5650008b2e747fe1809eeb5a1dde0e80850a", 0, "bouilli.txt" },
+		{ 0100644, "68af1fc7407fd9addf1701a87eb1c95c7494c598", 0, "oyster.txt" },
+		{ 0100644, "94d2c01087f48213bd157222d54edfefd77c9bba", 0, "veal.txt" },
+	};
+	size_t expected_cnt = sizeof(expected) / sizeof(struct merge_index_entry);
+
+	git_oid_fromstr(&oid, "539bd011c4822c560c1d17cab095006b7a10f707");
+	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
+
+	cl_git_pass(git_diff_from_buffer(&diff, diff_file, strlen(diff_file)));
+
+	cl_git_pass(git_reset(repo, (git_object *)commit, GIT_RESET_HARD, NULL));
+	cl_git_pass(git_apply(repo, diff, NULL));
+
+	validate_apply_workdir(repo, expected, expected_cnt);
+
+	git_diff_free(diff);
+	git_commit_free(commit);
+}