git/builtin/replay.c

/*
 * "git replay" builtin command
 */

#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"

#include "builtin.h"
#include "environment.h"
#include "hex.h"
#include "lockfile.h"
#include "merge-ort.h"
#include "object-name.h"
#include "parse-options.h"
#include "refs.h"
#include "replay.h"
#include "revision.h"
#include "strmap.h"
#include <oidset.h>
#include <tree.h>

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

	if (repo_get_oid(repo, name, &oid))
		return NULL;
	obj = parse_object(repo, &oid);
	return (struct commit *)repo_peel_to_type(repo, name, 0, obj,
						  OBJ_COMMIT);
}

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

static void get_ref_information(struct repository *repo,
				struct rev_cmdline_info *cmd_info,
				struct ref_info *ref_info)
{
	int i;

	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 (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 determine_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);
		if (rinfo.positive_refexprs <
		    strset_get_size(&rinfo.positive_refs))
			die(_("all positive revisions given must be references"));
	} else if (*advance_name) {
		struct object_id oid;
		char *fullname = NULL;

		*onto = peel_committish(repo, *advance_name);
		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"));
		}
		if (rinfo.positive_refexprs > 1)
			die(_("cannot advance target with multiple sources because ordering would be ill-defined"));
	} else {
		int positive_refs_complete = (
			rinfo.positive_refexprs ==
			strset_get_size(&rinfo.positive_refs));
		int negative_refs_complete = (
			rinfo.negative_refexprs ==
			strset_get_size(&rinfo.negative_refs));
		/*
		 * We need either positive_refs_complete or
		 * negative_refs_complete, but not both.
		 */
		if (rinfo.negative_refexprs > 0 &&
		    positive_refs_complete == negative_refs_complete)
			die(_("cannot implicitly determine whether this is an --advance or --onto operation"));
		if (negative_refs_complete) {
			struct hashmap_iter iter;
			struct strmap_entry *entry;
			const char *last_key = NULL;

			if (rinfo.negative_refexprs == 0)
				die(_("all positive revisions given must be references"));
			else if (rinfo.negative_refexprs > 1)
				die(_("cannot implicitly determine whether this is an --advance or --onto operation"));
			else if (rinfo.positive_refexprs > 1)
				die(_("cannot advance target with multiple source branches because ordering would be ill-defined"));

			/* Only one entry, but we have to loop to get it */
			strset_for_each_entry(&rinfo.negative_refs,
					      &iter, entry) {
				last_key = entry->key;
			}

			free(*advance_name);
			*advance_name = xstrdup_or_null(last_key);
		} else { /* positive_refs_complete */
			if (rinfo.negative_refexprs > 1)
				die(_("cannot implicitly determine correct base for --onto"));
			if (rinfo.negative_refexprs == 1)
				*onto = rinfo.onto;
		}
	}
	if (!*advance_name) {
		*update_refs = xcalloc(1, sizeof(**update_refs));
		**update_refs = rinfo.positive_refs;
		memset(&rinfo.positive_refs, 0, sizeof(**update_refs));
	}
	strset_clear(&rinfo.negative_refs);
	strset_clear(&rinfo.positive_refs);
}

static int add_ref_to_transaction(struct ref_transaction *transaction,
				  const char *refname,
				  const struct object_id *new_oid,
				  const struct object_id *old_oid,
				  struct strbuf *err)
{
	return ref_transaction_update(transaction, refname, new_oid, old_oid,
				      NULL, NULL, 0, "git replay", err);
}

static void print_rejected_update(const char *refname,
				  const struct object_id *old_oid UNUSED,
				  const struct object_id *new_oid UNUSED,
				  const char *old_target UNUSED,
				  const char *new_target UNUSED,
				  enum ref_transaction_error err,
				  void *cb_data UNUSED)
{
	const char *reason = ref_transaction_error_msg(err);
	warning(_("failed to update %s: %s"), refname, reason);
}

int cmd_replay(int argc,
	       const char **argv,
	       const char *prefix,
	       struct repository *repo)
{
	const char *advance_name_opt = NULL;
	char *advance_name = NULL;
	struct commit *onto = NULL;
	const char *onto_name = NULL;
	int contained = 0;
	int output_commands = 0;
	int allow_partial = 0;

	struct rev_info revs;
	struct commit *last_commit = NULL;
	struct commit *commit;
	struct merge_options merge_opt;
	struct merge_result result;
	struct strset *update_refs = NULL;
	kh_oid_map_t *replayed_commits;
	struct ref_transaction *transaction = NULL;
	struct strbuf transaction_err = STRBUF_INIT;
	int commits_processed = 0;
	int ret = 0;

	const char *const replay_usage[] = {
		N_("(EXPERIMENTAL!) git replay "
		   "([--contained] --onto <newbase> | --advance <branch>) "
		   "[--output-commands | --allow-partial] <revision-range>..."),
		NULL
	};
	struct option replay_options[] = {
		OPT_STRING(0, "advance", &advance_name_opt,
			   N_("branch"),
			   N_("make replay advance given branch")),
		OPT_STRING(0, "onto", &onto_name,
			   N_("revision"),
			   N_("replay onto given commit")),
		OPT_BOOL(0, "contained", &contained,
			 N_("advance all branches contained in revision-range")),
		OPT_BOOL(0, "output-commands", &output_commands,
			 N_("output update commands instead of updating refs")),
		OPT_BOOL(0, "allow-partial", &allow_partial,
			 N_("allow some ref updates to succeed even if others fail")),
		OPT_END()
	};

	argc = parse_options(argc, argv, prefix, replay_options, replay_usage,
			     PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_KEEP_UNKNOWN_OPT);

	if (!onto_name && !advance_name_opt) {
		error(_("option --onto or --advance is mandatory"));
		usage_with_options(replay_usage, replay_options);
	}

	die_for_incompatible_opt2(!!advance_name_opt, "--advance",
				  contained, "--contained");

	die_for_incompatible_opt2(allow_partial, "--allow-partial",
				  output_commands, "--output-commands");

	advance_name = xstrdup_or_null(advance_name_opt);

	repo_init_revisions(repo, &revs, prefix);

	/*
	 * Set desired values for rev walking options here. If they
	 * are changed by some user specified option in setup_revisions()
	 * below, we will detect that below and then warn.
	 *
	 * TODO: In the future we might want to either die(), or allow
	 * some options changing these values if we think they could
	 * be useful.
	 */
	revs.reverse = 1;
	revs.sort_order = REV_SORT_IN_GRAPH_ORDER;
	revs.topo_order = 1;
	revs.simplify_history = 0;

	argc = setup_revisions(argc, argv, &revs, NULL);
	if (argc > 1) {
		ret = error(_("unrecognized argument: %s"), argv[1]);
		goto cleanup;
	}

	/*
	 * Detect and warn if we override some user specified rev
	 * walking options.
	 */
	if (revs.reverse != 1) {
		warning(_("some rev walking options will be overridden as "
			  "'%s' bit in 'struct rev_info' will be forced"),
			"reverse");
		revs.reverse = 1;
	}
	if (revs.sort_order != REV_SORT_IN_GRAPH_ORDER) {
		warning(_("some rev walking options will be overridden as "
			  "'%s' bit in 'struct rev_info' will be forced"),
			"sort_order");
		revs.sort_order = REV_SORT_IN_GRAPH_ORDER;
	}
	if (revs.topo_order != 1) {
		warning(_("some rev walking options will be overridden as "
			  "'%s' bit in 'struct rev_info' will be forced"),
			"topo_order");
		revs.topo_order = 1;
	}
	if (revs.simplify_history != 0) {
		warning(_("some rev walking options will be overridden as "
			  "'%s' bit in 'struct rev_info' will be forced"),
			"simplify_history");
		revs.simplify_history = 0;
	}

	determine_replay_mode(repo, &revs.cmdline, onto_name, &advance_name,
			      &onto, &update_refs);

	if (!output_commands) {
		unsigned int transaction_flags = allow_partial ? REF_TRANSACTION_ALLOW_FAILURE : 0;
		transaction = ref_store_transaction_begin(get_main_ref_store(repo),
							  transaction_flags,
							  &transaction_err);
		if (!transaction) {
			ret = error(_("failed to begin ref transaction: %s"), transaction_err.buf);
			goto cleanup;
		}
	}

	if (!onto) /* FIXME: Should handle replaying down to root commit */
		die("Replaying down to root commit is not supported yet!");

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

	init_basic_merge_options(&merge_opt, repo);
	memset(&result, 0, sizeof(result));
	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;

		commits_processed = 1;

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

		last_commit = replay_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_name)
			continue;
		decoration = get_name_decoration(&commit->object);
		if (!decoration)
			continue;
		while (decoration) {
			if (decoration->type == DECORATION_REF_LOCAL &&
			    (contained || strset_contains(update_refs,
							  decoration->name))) {
				if (output_commands) {
					printf("update %s %s %s\n",
					       decoration->name,
					       oid_to_hex(&last_commit->object.oid),
					       oid_to_hex(&commit->object.oid));
				} else if (add_ref_to_transaction(transaction, decoration->name,
								  &last_commit->object.oid,
								  &commit->object.oid,
								  &transaction_err) < 0) {
					ret = error(_("failed to add ref update to transaction: %s"), transaction_err.buf);
					goto cleanup;
				}
			}
			decoration = decoration->next;
		}
	}

	/* In --advance mode, advance the target ref */
	if (result.clean == 1 && advance_name) {
		if (output_commands) {
			printf("update %s %s %s\n",
			       advance_name,
			       oid_to_hex(&last_commit->object.oid),
			       oid_to_hex(&onto->object.oid));
		} else if (add_ref_to_transaction(transaction, advance_name,
						  &last_commit->object.oid,
						  &onto->object.oid,
						  &transaction_err) < 0) {
			ret = error(_("failed to add ref update to transaction: %s"), transaction_err.buf);
			goto cleanup;
		}
	}

	/* Commit the ref transaction if we have one */
	if (transaction && result.clean == 1) {
		if (ref_transaction_commit(transaction, &transaction_err)) {
			if (allow_partial) {
				warning(_("some ref updates failed: %s"), transaction_err.buf);
				ref_transaction_for_each_rejected_update(transaction,
									 print_rejected_update, NULL);
				ret = 0; /* Set failure even with allow_partial */
			} else {
				ret = error(_("failed to update refs: %s"), transaction_err.buf);
				goto cleanup;
			}
		}
	}

	merge_finalize(&merge_opt, &result);
	kh_destroy_oid_map(replayed_commits);
	if (update_refs) {
		strset_clear(update_refs);
		free(update_refs);
	}

	/* Handle empty ranges: if no commits were processed, treat as success */
	if (!commits_processed)
		ret = 1; /* Success - no commits to replay is not an error */
	else
		ret = result.clean;

cleanup:
	if (transaction)
		ref_transaction_free(transaction);
	strbuf_release(&transaction_err);
	release_revisions(&revs);
	free(advance_name);

	/* Return */
	if (ret < 0)
		exit(128);
	return ret ? 0 : 1;
}