git/replay.c

#define USE_THE_REPOSITORY_VARIABLE

#include "git-compat-util.h"
#include "environment.h"
#include "hex.h"
#include "merge-ort.h"
#include "object-name.h"
#include "oidset.h"
#include "parse-options.h"
#include "refs.h"
#include "replay.h"
#include "revision.h"
#include "tree.h"

static const char *short_commit_name(struct repository *repo,
				     struct commit *commit)
{
	return repo_find_unique_abbrev(repo, &commit->object.oid,
				       DEFAULT_ABBREV);
}

static struct commit *peel_committish(struct repository *repo,
				      const char *name,
				      const char *mode)
{
	struct object *obj;
	struct object_id oid;

	if (repo_get_oid(repo, name, &oid))
		die(_("'%s' is not a valid commit-ish for %s"), name, mode);
	obj = parse_object_or_die(repo, &oid, name);
	return (struct commit *)repo_peel_to_type(repo, name, 0, obj,
						  OBJ_COMMIT);
}

static char *get_author(const char *message)
{
	size_t len;
	const char *a;

	a = find_commit_header(message, "author", &len);
	if (a)
		return xmemdupz(a, len);

	return NULL;
}

static struct commit *create_commit(struct repository *repo,
				    struct tree *tree,
				    struct commit *based_on,
				    struct commit *parent)
{
	struct object_id ret;
	struct object *obj = NULL;
	struct commit_list *parents = NULL;
	char *author;
	char *sign_commit = NULL; /* FIXME: cli users might want to sign again */
	struct commit_extra_header *extra = NULL;
	struct strbuf msg = STRBUF_INIT;
	const char *out_enc = get_commit_output_encoding();
	const char *message = repo_logmsg_reencode(repo, based_on,
						   NULL, out_enc);
	const char *orig_message = NULL;
	const char *exclude_gpgsig[] = { "gpgsig", "gpgsig-sha256", NULL };

	commit_list_insert(parent, &parents);
	extra = read_commit_extra_headers(based_on, exclude_gpgsig);
	find_commit_subject(message, &orig_message);
	strbuf_addstr(&msg, orig_message);
	author = get_author(message);
	reset_ident_date();
	if (commit_tree_extended(msg.buf, msg.len, &tree->object.oid, parents,
				 &ret, author, NULL, sign_commit, extra)) {
		error(_("failed to write commit object"));
		goto out;
	}

	obj = parse_object(repo, &ret);

out:
	repo_unuse_commit_buffer(repo, based_on, message);
	free_commit_extra_headers(extra);
	free_commit_list(parents);
	strbuf_release(&msg);
	free(author);
	return (struct commit *)obj;
}

struct ref_info {
	struct commit *onto;
	struct strset positive_refs;
	struct strset negative_refs;
	size_t positive_refexprs;
	size_t negative_refexprs;
};

static void get_ref_information(struct repository *repo,
				struct rev_cmdline_info *cmd_info,
				struct ref_info *ref_info)
{
	ref_info->onto = NULL;
	strset_init(&ref_info->positive_refs);
	strset_init(&ref_info->negative_refs);
	ref_info->positive_refexprs = 0;
	ref_info->negative_refexprs = 0;

	/*
	 * When the user specifies e.g.
	 *   git replay origin/main..mybranch
	 *   git replay ^origin/next mybranch1 mybranch2
	 * we want to be able to determine where to replay the commits.  In
	 * these examples, the branches are probably based on an old version
	 * of either origin/main or origin/next, so we want to replay on the
	 * newest version of that branch.  In contrast we would want to error
	 * out if they ran
	 *   git replay ^origin/master ^origin/next mybranch
	 *   git replay mybranch~2..mybranch
	 * the first of those because there's no unique base to choose, and
	 * the second because they'd likely just be replaying commits on top
	 * of the same commit and not making any difference.
	 */
	for (size_t i = 0; i < cmd_info->nr; i++) {
		struct rev_cmdline_entry *e = cmd_info->rev + i;
		struct object_id oid;
		const char *refexpr = e->name;
		char *fullname = NULL;
		int can_uniquely_dwim = 1;

		if (*refexpr == '^')
			refexpr++;
		if (repo_dwim_ref(repo, refexpr, strlen(refexpr), &oid, &fullname, 0) != 1)
			can_uniquely_dwim = 0;

		if (e->flags & BOTTOM) {
			if (can_uniquely_dwim)
				strset_add(&ref_info->negative_refs, fullname);
			if (!ref_info->negative_refexprs)
				ref_info->onto = lookup_commit_reference_gently(repo,
										&e->item->oid, 1);
			ref_info->negative_refexprs++;
		} else {
			if (can_uniquely_dwim)
				strset_add(&ref_info->positive_refs, fullname);
			ref_info->positive_refexprs++;
		}

		free(fullname);
	}
}

static void set_up_replay_mode(struct repository *repo,
			       struct rev_cmdline_info *cmd_info,
			       const char *onto_name,
			       char **advance_name,
			       struct commit **onto,
			       struct strset **update_refs)
{
	struct ref_info rinfo;

	get_ref_information(repo, cmd_info, &rinfo);
	if (!rinfo.positive_refexprs)
		die(_("need some commits to replay"));

	die_for_incompatible_opt2(!!onto_name, "--onto",
				  !!*advance_name, "--advance");
	if (onto_name) {
		*onto = peel_committish(repo, onto_name, "--onto");
		if (rinfo.positive_refexprs <
		    strset_get_size(&rinfo.positive_refs))
			die(_("all positive revisions given must be references"));
		*update_refs = xcalloc(1, sizeof(**update_refs));
		**update_refs = rinfo.positive_refs;
		memset(&rinfo.positive_refs, 0, sizeof(**update_refs));
	} else {
		struct object_id oid;
		char *fullname = NULL;

		if (!*advance_name)
			BUG("expected either onto_name or *advance_name in this function");

		if (repo_dwim_ref(repo, *advance_name, strlen(*advance_name),
			     &oid, &fullname, 0) == 1) {
			free(*advance_name);
			*advance_name = fullname;
		} else {
			die(_("argument to --advance must be a reference"));
		}
		*onto = peel_committish(repo, *advance_name, "--advance");
		if (rinfo.positive_refexprs > 1)
			die(_("cannot advance target with multiple sources because ordering would be ill-defined"));
	}
	strset_clear(&rinfo.negative_refs);
	strset_clear(&rinfo.positive_refs);
}

static struct commit *mapped_commit(kh_oid_map_t *replayed_commits,
				    struct commit *commit,
				    struct commit *fallback)
{
	khint_t pos = kh_get_oid_map(replayed_commits, commit->object.oid);
	if (pos == kh_end(replayed_commits))
		return fallback;
	return kh_value(replayed_commits, pos);
}

static struct commit *pick_regular_commit(struct repository *repo,
					  struct commit *pickme,
					  kh_oid_map_t *replayed_commits,
					  struct commit *onto,
					  struct merge_options *merge_opt,
					  struct merge_result *result)
{
	struct commit *base, *replayed_base;
	struct tree *pickme_tree, *base_tree, *replayed_base_tree;

	base = pickme->parents->item;
	replayed_base = mapped_commit(replayed_commits, base, onto);

	replayed_base_tree = repo_get_commit_tree(repo, replayed_base);
	pickme_tree = repo_get_commit_tree(repo, pickme);
	base_tree = repo_get_commit_tree(repo, base);

	merge_opt->branch1 = short_commit_name(repo, replayed_base);
	merge_opt->branch2 = short_commit_name(repo, pickme);
	merge_opt->ancestor = xstrfmt("parent of %s", merge_opt->branch2);

	merge_incore_nonrecursive(merge_opt,
				  base_tree,
				  replayed_base_tree,
				  pickme_tree,
				  result);

	free((char*)merge_opt->ancestor);
	merge_opt->ancestor = NULL;
	if (!result->clean)
		return NULL;
	/* Drop commits that become empty */
	if (oideq(&replayed_base_tree->object.oid, &result->tree->object.oid) &&
	    !oideq(&pickme_tree->object.oid, &base_tree->object.oid))
		return replayed_base;
	return create_commit(repo, result->tree, pickme, replayed_base);
}

void replay_result_release(struct replay_result *result)
{
	for (size_t i = 0; i < result->updates_nr; i++)
		free(result->updates[i].refname);
	free(result->updates);
}

static void replay_result_queue_update(struct replay_result *result,
				       const char *refname,
				       const struct object_id *old_oid,
				       const struct object_id *new_oid)
{
	ALLOC_GROW(result->updates, result->updates_nr + 1, result->updates_alloc);
	result->updates[result->updates_nr].refname = xstrdup(refname);
	result->updates[result->updates_nr].old_oid = *old_oid;
	result->updates[result->updates_nr].new_oid = *new_oid;
	result->updates_nr++;
}

int replay_revisions(struct repository *repo, struct rev_info *revs,
		     struct replay_revisions_options *opts,
		     struct replay_result *out)
{
	kh_oid_map_t *replayed_commits = NULL;
	struct strset *update_refs = NULL;
	struct commit *last_commit = NULL;
	struct commit *commit;
	struct commit *onto = NULL;
	struct merge_options merge_opt;
	struct merge_result result = {
		.clean = 1,
	};
	char *advance;
	int ret;

	advance = xstrdup_or_null(opts->advance);
	set_up_replay_mode(repo, &revs->cmdline, opts->onto, &advance,
			   &onto, &update_refs);

	/* FIXME: Should allow replaying commits with the first as a root commit */

	if (prepare_revision_walk(revs) < 0) {
		ret = error(_("error preparing revisions"));
		goto out;
	}

	init_basic_merge_options(&merge_opt, repo);
	merge_opt.show_rename_progress = 0;
	last_commit = onto;
	replayed_commits = kh_init_oid_map();
	while ((commit = get_revision(revs))) {
		const struct name_decoration *decoration;
		khint_t pos;
		int hr;

		if (!commit->parents)
			die(_("replaying down from root commit is not supported yet!"));
		if (commit->parents->next)
			die(_("replaying merge commits is not supported yet!"));

		last_commit = pick_regular_commit(repo, commit, replayed_commits,
						  onto, &merge_opt, &result);
		if (!last_commit)
			break;

		/* Record commit -> last_commit mapping */
		pos = kh_put_oid_map(replayed_commits, commit->object.oid, &hr);
		if (hr == 0)
			BUG("Duplicate rewritten commit: %s\n",
			    oid_to_hex(&commit->object.oid));
		kh_value(replayed_commits, pos) = last_commit;

		/* Update any necessary branches */
		if (advance)
			continue;
		decoration = get_name_decoration(&commit->object);
		if (!decoration)
			continue;
		while (decoration) {
			if (decoration->type == DECORATION_REF_LOCAL &&
			    (opts->contained || strset_contains(update_refs,
								decoration->name))) {
				replay_result_queue_update(out, decoration->name,
							   &commit->object.oid,
							   &last_commit->object.oid);
			}
			decoration = decoration->next;
		}
	}

	if (!result.clean) {
		out->merge_conflict = true;
		ret = -1;
		goto out;
	}

	/* In --advance mode, advance the target ref */
	if (advance)
		replay_result_queue_update(out, advance,
					   &onto->object.oid,
					   &last_commit->object.oid);

	out->final_oid = last_commit->object.oid;

	ret = 0;

out:
	if (update_refs) {
		strset_clear(update_refs);
		free(update_refs);
	}
	kh_destroy_oid_map(replayed_commits);
	merge_finalize(&merge_opt, &result);
	free(advance);
	return ret;
}