Function write_index_patch

builtin/am.c:1426–1453

* Writes the diff of the index against HEAD as a patch to the state * directory's "patch" file. */

 * directory's "patch" file.
 */
static void write_index_patch(const struct am_state *state)
{
	struct tree *tree;
	struct object_id head;
	struct rev_info rev_info;
	FILE *fp;

	if (!repo_get_oid(the_repository, "HEAD", &head)) {
		struct commit *commit = lookup_commit_or_die(&head, "HEAD");
		tree = repo_get_commit_tree(the_repository, commit);
	} else
		tree = lookup_tree(the_repository,
				   the_repository->hash_algo->empty_tree);

	fp = xfopen(am_path(state, "patch"), "w");
	repo_init_revisions(the_repository, &rev_info, NULL);
	rev_info.diff = 1;
	rev_info.disable_stdin = 1;
	rev_info.no_commit_id = 1;
	rev_info.diffopt.output_format = DIFF_FORMAT_PATCH;
	rev_info.diffopt.use_color = GIT_COLOR_NEVER;
	rev_info.diffopt.file = fp;
	rev_info.diffopt.close_file = 1;
	add_pending_object(&rev_info, &tree->object, "");
	diff_setup_done(&rev_info.diffopt);
	run_diff_index(&rev_info, DIFF_INDEX_CACHED);
	release_revisions(&rev_info);
}

/**
 * Like parse_mail(), but parses the mail by looking up its commit ID