Turn `git bisect` into a full built-in

Now that the shell script hands off to the `bisect--helper` to do
_anything_ (except to show the help), it is but a tiny step to let the
helper implement the actual `git bisect` command instead.

This retires `git-bisect.sh`, concluding a multi-year journey that many
hands helped with, in particular Pranit Bauna, Tanushree Tumane and
Miriam Rubio.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>

1 files changed, 1451 insertions, 0 deletions

diff --git a/builtin/bisect.c b/builtin/bisect.c
new file mode 100644
index 0000000000..cc9483e851
--- /dev/null
+++ b/builtin/bisect.c
@@ -0,0 +1,1451 @@
+#include "builtin.h"
+#include "cache.h"
+#include "parse-options.h"
+#include "bisect.h"
+#include "refs.h"
+#include "dir.h"
+#include "strvec.h"
+#include "run-command.h"
+#include "prompt.h"
+#include "quote.h"
+#include "revision.h"
+
+static GIT_PATH_FUNC(git_path_bisect_terms, "BISECT_TERMS")
+static GIT_PATH_FUNC(git_path_bisect_expected_rev, "BISECT_EXPECTED_REV")
+static GIT_PATH_FUNC(git_path_bisect_ancestors_ok, "BISECT_ANCESTORS_OK")
+static GIT_PATH_FUNC(git_path_bisect_start, "BISECT_START")
+static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
+static GIT_PATH_FUNC(git_path_head_name, "head-name")
+static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
+static GIT_PATH_FUNC(git_path_bisect_first_parent, "BISECT_FIRST_PARENT")
+static GIT_PATH_FUNC(git_path_bisect_run, "BISECT_RUN")
+
+#define BUILTIN_GIT_BISECT_START_USAGE \
+	N_("git bisect start [--term-{new,bad}=<term> --term-{old,good}=<term>]" \
+	   "    [--no-checkout] [--first-parent] [<bad> [<good>...]] [--]" \
+	   "    [<pathspec>...]")
+#define BUILTIN_GIT_BISECT_STATE_USAGE \
+	N_("git bisect (good|bad) [<rev>...]")
+#define BUILTIN_GIT_BISECT_TERMS_USAGE \
+	"git bisect terms [--term-good | --term-bad]"
+#define BUILTIN_GIT_BISECT_SKIP_USAGE \
+	N_("git bisect skip [(<rev>|<range>)...]")
+#define BUILTIN_GIT_BISECT_NEXT_USAGE \
+	"git bisect next"
+#define BUILTIN_GIT_BISECT_RESET_USAGE \
+	N_("git bisect reset [<commit>]")
+#define BUILTIN_GIT_BISECT_VISUALIZE_USAGE \
+	"git bisect visualize"
+#define BUILTIN_GIT_BISECT_REPLAY_USAGE \
+	N_("git bisect replay <logfile>")
+#define BUILTIN_GIT_BISECT_LOG_USAGE \
+	"git bisect log"
+#define BUILTIN_GIT_BISECT_RUN_USAGE \
+	N_("git bisect run <cmd>...")
+
+static const char * const git_bisect_usage[] = {
+	BUILTIN_GIT_BISECT_START_USAGE,
+	BUILTIN_GIT_BISECT_STATE_USAGE,
+	BUILTIN_GIT_BISECT_TERMS_USAGE,
+	BUILTIN_GIT_BISECT_SKIP_USAGE,
+	BUILTIN_GIT_BISECT_NEXT_USAGE,
+	BUILTIN_GIT_BISECT_RESET_USAGE,
+	BUILTIN_GIT_BISECT_VISUALIZE_USAGE,
+	BUILTIN_GIT_BISECT_REPLAY_USAGE,
+	BUILTIN_GIT_BISECT_LOG_USAGE,
+	BUILTIN_GIT_BISECT_RUN_USAGE,
+	NULL
+};
+
+struct add_bisect_ref_data {
+	struct rev_info *revs;
+	unsigned int object_flags;
+};
+
+struct bisect_terms {
+	char *term_good;
+	char *term_bad;
+};
+
+static void free_terms(struct bisect_terms *terms)
+{
+	FREE_AND_NULL(terms->term_good);
+	FREE_AND_NULL(terms->term_bad);
+}
+
+static void set_terms(struct bisect_terms *terms, const char *bad,
+		      const char *good)
+{
+	free((void *)terms->term_good);
+	terms->term_good = xstrdup(good);
+	free((void *)terms->term_bad);
+	terms->term_bad = xstrdup(bad);
+}
+
+static const char vocab_bad[] = "bad|new";
+static const char vocab_good[] = "good|old";
+
+static int bisect_autostart(struct bisect_terms *terms);
+
+/*
+ * Check whether the string `term` belongs to the set of strings
+ * included in the variable arguments.
+ */
+LAST_ARG_MUST_BE_NULL
+static int one_of(const char *term, ...)
+{
+	int res = 0;
+	va_list matches;
+	const char *match;
+
+	va_start(matches, term);
+	while (!res && (match = va_arg(matches, const char *)))
+		res = !strcmp(term, match);
+	va_end(matches);
+
+	return res;
+}
+
+/*
+ * return code BISECT_INTERNAL_SUCCESS_MERGE_BASE
+ * and BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND are codes
+ * that indicate special success.
+ */
+
+static int is_bisect_success(enum bisect_error res)
+{
+	return !res ||
+		res == BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND ||
+		res == BISECT_INTERNAL_SUCCESS_MERGE_BASE;
+}
+
+static int write_in_file(const char *path, const char *mode, const char *format, va_list args)
+{
+	FILE *fp = NULL;
+	int res = 0;
+
+	if (strcmp(mode, "w") && strcmp(mode, "a"))
+		BUG("write-in-file does not support '%s' mode", mode);
+	fp = fopen(path, mode);
+	if (!fp)
+		return error_errno(_("cannot open file '%s' in mode '%s'"), path, mode);
+	res = vfprintf(fp, format, args);
+
+	if (res < 0) {
+		int saved_errno = errno;
+		fclose(fp);
+		errno = saved_errno;
+		return error_errno(_("could not write to file '%s'"), path);
+	}
+
+	return fclose(fp);
+}
+
+__attribute__((format (printf, 2, 3)))
+static int write_to_file(const char *path, const char *format, ...)
+{
+	int res;
+	va_list args;
+
+	va_start(args, format);
+	res = write_in_file(path, "w", format, args);
+	va_end(args);
+
+	return res;
+}
+
+__attribute__((format (printf, 2, 3)))
+static int append_to_file(const char *path, const char *format, ...)
+{
+	int res;
+	va_list args;
+
+	va_start(args, format);
+	res = write_in_file(path, "a", format, args);
+	va_end(args);
+
+	return res;
+}
+
+static int print_file_to_stdout(const char *path)
+{
+	int fd = open(path, O_RDONLY);
+	int ret = 0;
+
+	if (fd < 0)
+		return error_errno(_("cannot open file '%s' for reading"), path);
+	if (copy_fd(fd, 1) < 0)
+		ret = error_errno(_("failed to read '%s'"), path);
+	close(fd);
+	return ret;
+}
+
+static int check_term_format(const char *term, const char *orig_term)
+{
+	int res;
+	char *new_term = xstrfmt("refs/bisect/%s", term);
+
+	res = check_refname_format(new_term, 0);
+	free(new_term);
+
+	if (res)
+		return error(_("'%s' is not a valid term"), term);
+
+	if (one_of(term, "help", "start", "skip", "next", "reset",
+			"visualize", "view", "replay", "log", "run", "terms", NULL))
+		return error(_("can't use the builtin command '%s' as a term"), term);
+
+	/*
+	 * In theory, nothing prevents swapping completely good and bad,
+	 * but this situation could be confusing and hasn't been tested
+	 * enough. Forbid it for now.
+	 */
+
+	if ((strcmp(orig_term, "bad") && one_of(term, "bad", "new", NULL)) ||
+		 (strcmp(orig_term, "good") && one_of(term, "good", "old", NULL)))
+		return error(_("can't change the meaning of the term '%s'"), term);
+
+	return 0;
+}
+
+static int write_terms(const char *bad, const char *good)
+{
+	int res;
+
+	if (!strcmp(bad, good))
+		return error(_("please use two different terms"));
+
+	if (check_term_format(bad, "bad") || check_term_format(good, "good"))
+		return -1;
+
+	res = write_to_file(git_path_bisect_terms(), "%s\n%s\n", bad, good);
+
+	return res;
+}
+
+static int bisect_reset(const char *commit)
+{
+	struct strbuf branch = STRBUF_INIT;
+
+	if (!commit) {
+		if (strbuf_read_file(&branch, git_path_bisect_start(), 0) < 1) {
+			printf(_("We are not bisecting.\n"));
+			return 0;
+		}
+		strbuf_rtrim(&branch);
+	} else {
+		struct object_id oid;
+
+		if (get_oid_commit(commit, &oid))
+			return error(_("'%s' is not a valid commit"), commit);
+		strbuf_addstr(&branch, commit);
+	}
+
+	if (!ref_exists("BISECT_HEAD")) {
+		struct child_process cmd = CHILD_PROCESS_INIT;
+
+		cmd.git_cmd = 1;
+		strvec_pushl(&cmd.args, "checkout", branch.buf, "--", NULL);
+		if (run_command(&cmd)) {
+			error(_("could not check out original"
+				" HEAD '%s'. Try 'git bisect"
+				" reset <commit>'."), branch.buf);
+			strbuf_release(&branch);
+			return -1;
+		}
+	}
+
+	strbuf_release(&branch);
+	return bisect_clean_state();
+}
+
+static void log_commit(FILE *fp, char *fmt, const char *state,
+		       struct commit *commit)
+{
+	struct pretty_print_context pp = {0};
+	struct strbuf commit_msg = STRBUF_INIT;
+	char *label = xstrfmt(fmt, state);
+
+	format_commit_message(commit, "%s", &commit_msg, &pp);
+
+	fprintf(fp, "# %s: [%s] %s\n", label, oid_to_hex(&commit->object.oid),
+		commit_msg.buf);
+
+	strbuf_release(&commit_msg);
+	free(label);
+}
+
+static int bisect_write(const char *state, const char *rev,
+			const struct bisect_terms *terms, int nolog)
+{
+	struct strbuf tag = STRBUF_INIT;
+	struct object_id oid;
+	struct commit *commit;
+	FILE *fp = NULL;
+	int res = 0;
+
+	if (!strcmp(state, terms->term_bad)) {
+		strbuf_addf(&tag, "refs/bisect/%s", state);
+	} else if (one_of(state, terms->term_good, "skip", NULL)) {
+		strbuf_addf(&tag, "refs/bisect/%s-%s", state, rev);
+	} else {
+		res = error(_("Bad bisect_write argument: %s"), state);
+		goto finish;
+	}
+
+	if (get_oid(rev, &oid)) {
+		res = error(_("couldn't get the oid of the rev '%s'"), rev);
+		goto finish;
+	}
+
+	if (update_ref(NULL, tag.buf, &oid, NULL, 0,
+		       UPDATE_REFS_MSG_ON_ERR)) {
+		res = -1;
+		goto finish;
+	}
+
+	fp = fopen(git_path_bisect_log(), "a");
+	if (!fp) {
+		res = error_errno(_("couldn't open the file '%s'"), git_path_bisect_log());
+		goto finish;
+	}
+
+	commit = lookup_commit_reference(the_repository, &oid);
+	log_commit(fp, "%s", state, commit);
+
+	if (!nolog)
+		fprintf(fp, "git bisect %s %s\n", state, rev);
+
+finish:
+	if (fp)
+		fclose(fp);
+	strbuf_release(&tag);
+	return res;
+}
+
+static int check_and_set_terms(struct bisect_terms *terms, const char *cmd)
+{
+	int has_term_file = !is_empty_or_missing_file(git_path_bisect_terms());
+
+	if (one_of(cmd, "skip", "start", "terms", NULL))
+		return 0;
+
+	if (has_term_file && strcmp(cmd, terms->term_bad) &&
+	    strcmp(cmd, terms->term_good))
+		return error(_("Invalid command: you're currently in a "
+				"%s/%s bisect"), terms->term_bad,
+				terms->term_good);
+
+	if (!has_term_file) {
+		if (one_of(cmd, "bad", "good", NULL)) {
+			set_terms(terms, "bad", "good");
+			return write_terms(terms->term_bad, terms->term_good);
+		}
+		if (one_of(cmd, "new", "old", NULL)) {
+			set_terms(terms, "new", "old");
+			return write_terms(terms->term_bad, terms->term_good);
+		}
+	}
+
+	return 0;
+}
+
+static int inc_nr(const char *refname UNUSED,
+		  const struct object_id *oid UNUSED,
+		  int flag UNUSED, void *cb_data)
+{
+	unsigned int *nr = (unsigned int *)cb_data;
+	(*nr)++;
+	return 0;
+}
+
+static const char need_bad_and_good_revision_warning[] =
+	N_("You need to give me at least one %s and %s revision.\n"
+	   "You can use \"git bisect %s\" and \"git bisect %s\" for that.");
+
+static const char need_bisect_start_warning[] =
+	N_("You need to start by \"git bisect start\".\n"
+	   "You then need to give me at least one %s and %s revision.\n"
+	   "You can use \"git bisect %s\" and \"git bisect %s\" for that.");
+
+static int decide_next(const struct bisect_terms *terms,
+		       const char *current_term, int missing_good,
+		       int missing_bad)
+{
+	if (!missing_good && !missing_bad)
+		return 0;
+	if (!current_term)
+		return -1;
+
+	if (missing_good && !missing_bad &&
+	    !strcmp(current_term, terms->term_good)) {
+		char *yesno;
+		/*
+		 * have bad (or new) but not good (or old). We could bisect
+		 * although this is less optimum.
+		 */
+		warning(_("bisecting only with a %s commit"), terms->term_bad);
+		if (!isatty(0))
+			return 0;
+		/*
+		 * TRANSLATORS: Make sure to include [Y] and [n] in your
+		 * translation. The program will only accept English input
+		 * at this point.
+		 */
+		yesno = git_prompt(_("Are you sure [Y/n]? "), PROMPT_ECHO);
+		if (starts_with(yesno, "N") || starts_with(yesno, "n"))
+			return -1;
+		return 0;
+	}
+
+	if (!is_empty_or_missing_file(git_path_bisect_start()))
+		return error(_(need_bad_and_good_revision_warning),
+			     vocab_bad, vocab_good, vocab_bad, vocab_good);
+	else
+		return error(_(need_bisect_start_warning),
+			     vocab_good, vocab_bad, vocab_good, vocab_bad);
+}
+
+static void bisect_status(struct bisect_state *state,
+			  const struct bisect_terms *terms)
+{
+	char *bad_ref = xstrfmt("refs/bisect/%s", terms->term_bad);
+	char *good_glob = xstrfmt("%s-*", terms->term_good);
+
+	if (ref_exists(bad_ref))
+		state->nr_bad = 1;
+
+	for_each_glob_ref_in(inc_nr, good_glob, "refs/bisect/",
+			     (void *) &state->nr_good);
+
+	free(good_glob);
+	free(bad_ref);
+}
+
+__attribute__((format (printf, 1, 2)))
+static void bisect_log_printf(const char *fmt, ...)
+{
+	struct strbuf buf = STRBUF_INIT;
+	va_list ap;
+
+	va_start(ap, fmt);
+	strbuf_vaddf(&buf, fmt, ap);
+	va_end(ap);
+
+	printf("%s", buf.buf);
+	append_to_file(git_path_bisect_log(), "# %s", buf.buf);
+
+	strbuf_release(&buf);
+}
+
+static void bisect_print_status(const struct bisect_terms *terms)
+{
+	struct bisect_state state = { 0 };
+
+	bisect_status(&state, terms);
+
+	/* If we had both, we'd already be started, and shouldn't get here. */
+	if (state.nr_good && state.nr_bad)
+		return;
+
+	if (!state.nr_good && !state.nr_bad)
+		bisect_log_printf(_("status: waiting for both good and bad commits\n"));
+	else if (state.nr_good)
+		bisect_log_printf(Q_("status: waiting for bad commit, %d good commit known\n",
+				     "status: waiting for bad commit, %d good commits known\n",
+				     state.nr_good), state.nr_good);
+	else
+		bisect_log_printf(_("status: waiting for good commit(s), bad commit known\n"));
+}
+
+static int bisect_next_check(const struct bisect_terms *terms,
+			     const char *current_term)
+{
+	struct bisect_state state = { 0 };
+	bisect_status(&state, terms);
+	return decide_next(terms, current_term, !state.nr_good, !state.nr_bad);
+}
+
+static int get_terms(struct bisect_terms *terms)
+{
+	struct strbuf str = STRBUF_INIT;
+	FILE *fp = NULL;
+	int res = 0;
+
+	fp = fopen(git_path_bisect_terms(), "r");
+	if (!fp) {
+		res = -1;
+		goto finish;
+	}
+
+	free_terms(terms);
+	strbuf_getline_lf(&str, fp);
+	terms->term_bad = strbuf_detach(&str, NULL);
+	strbuf_getline_lf(&str, fp);
+	terms->term_good = strbuf_detach(&str, NULL);
+
+finish:
+	if (fp)
+		fclose(fp);
+	strbuf_release(&str);
+	return res;
+}
+
+static int bisect_terms(struct bisect_terms *terms, const char *option)
+{
+	if (get_terms(terms))
+		return error(_("no terms defined"));
+
+	if (!option) {
+		printf(_("Your current terms are %s for the old state\n"
+			 "and %s for the new state.\n"),
+		       terms->term_good, terms->term_bad);
+		return 0;
+	}
+	if (one_of(option, "--term-good", "--term-old", NULL))
+		printf("%s\n", terms->term_good);
+	else if (one_of(option, "--term-bad", "--term-new", NULL))
+		printf("%s\n", terms->term_bad);
+	else
+		return error(_("invalid argument %s for 'git bisect terms'.\n"
+			       "Supported options are: "
+			       "--term-good|--term-old and "
+			       "--term-bad|--term-new."), option);
+
+	return 0;
+}
+
+static int bisect_append_log_quoted(const char **argv)
+{
+	int res = 0;
+	FILE *fp = fopen(git_path_bisect_log(), "a");
+	struct strbuf orig_args = STRBUF_INIT;
+
+	if (!fp)
+		return -1;
+
+	if (fprintf(fp, "git bisect start") < 1) {
+		res = -1;
+		goto finish;
+	}
+
+	sq_quote_argv(&orig_args, argv);
+	if (fprintf(fp, "%s\n", orig_args.buf) < 1)
+		res = -1;
+
+finish:
+	fclose(fp);
+	strbuf_release(&orig_args);
+	return res;
+}
+
+static int add_bisect_ref(const char *refname, const struct object_id *oid,
+			  int flags UNUSED, void *cb)
+{
+	struct add_bisect_ref_data *data = cb;
+
+	add_pending_oid(data->revs, refname, oid, data->object_flags);
+
+	return 0;
+}
+
+static int prepare_revs(struct bisect_terms *terms, struct rev_info *revs)
+{
+	int res = 0;
+	struct add_bisect_ref_data cb = { revs };
+	char *good = xstrfmt("%s-*", terms->term_good);
+
+	/*
+	 * We cannot use terms->term_bad directly in
+	 * for_each_glob_ref_in() and we have to append a '*' to it,
+	 * otherwise for_each_glob_ref_in() will append '/' and '*'.
+	 */
+	char *bad = xstrfmt("%s*", terms->term_bad);
+
+	/*
+	 * It is important to reset the flags used by revision walks
+	 * as the previous call to bisect_next_all() in turn
+	 * sets up a revision walk.
+	 */
+	reset_revision_walk();
+	init_revisions(revs, NULL);
+	setup_revisions(0, NULL, revs, NULL);
+	for_each_glob_ref_in(add_bisect_ref, bad, "refs/bisect/", &cb);
+	cb.object_flags = UNINTERESTING;
+	for_each_glob_ref_in(add_bisect_ref, good, "refs/bisect/", &cb);
+	if (prepare_revision_walk(revs))
+		res = error(_("revision walk setup failed\n"));
+
+	free(good);
+	free(bad);
+	return res;
+}
+
+static int bisect_skipped_commits(struct bisect_terms *terms)
+{
+	int res;
+	FILE *fp = NULL;
+	struct rev_info revs;
+	struct commit *commit;
+	struct pretty_print_context pp = {0};
+	struct strbuf commit_name = STRBUF_INIT;
+
+	res = prepare_revs(terms, &revs);
+	if (res)
+		return res;
+
+	fp = fopen(git_path_bisect_log(), "a");
+	if (!fp)
+		return error_errno(_("could not open '%s' for appending"),
+				  git_path_bisect_log());
+
+	if (fprintf(fp, "# only skipped commits left to test\n") < 0)
+		return error_errno(_("failed to write to '%s'"), git_path_bisect_log());
+
+	while ((commit = get_revision(&revs)) != NULL) {
+		strbuf_reset(&commit_name);
+		format_commit_message(commit, "%s",
+				      &commit_name, &pp);
+		fprintf(fp, "# possible first %s commit: [%s] %s\n",
+			terms->term_bad, oid_to_hex(&commit->object.oid),
+			commit_name.buf);
+	}
+
+	/*
+	 * Reset the flags used by revision walks in case
+	 * there is another revision walk after this one.
+	 */
+	reset_revision_walk();
+
+	strbuf_release(&commit_name);
+	release_revisions(&revs);
+	fclose(fp);
+	return 0;
+}
+
+static int bisect_successful(struct bisect_terms *terms)
+{
+	struct object_id oid;
+	struct commit *commit;
+	struct pretty_print_context pp = {0};
+	struct strbuf commit_name = STRBUF_INIT;
+	char *bad_ref = xstrfmt("refs/bisect/%s",terms->term_bad);
+	int res;
+
+	read_ref(bad_ref, &oid);
+	commit = lookup_commit_reference_by_name(bad_ref);
+	format_commit_message(commit, "%s", &commit_name, &pp);
+
+	res = append_to_file(git_path_bisect_log(), "# first %s commit: [%s] %s\n",
+			    terms->term_bad, oid_to_hex(&commit->object.oid),
+			    commit_name.buf);
+
+	strbuf_release(&commit_name);
+	free(bad_ref);
+	return res;
+}
+
+static enum bisect_error bisect_next(struct bisect_terms *terms, const char *prefix)
+{
+	enum bisect_error res;
+
+	if (bisect_autostart(terms))
+		return BISECT_FAILED;
+
+	if (bisect_next_check(terms, terms->term_good))
+		return BISECT_FAILED;
+
+	/* Perform all bisection computation */
+	res = bisect_next_all(the_repository, prefix);
+
+	if (res == BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND) {
+		res = bisect_successful(terms);
+		return res ? res : BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND;
+	} else if (res == BISECT_ONLY_SKIPPED_LEFT) {
+		res = bisect_skipped_commits(terms);
+		return res ? res : BISECT_ONLY_SKIPPED_LEFT;
+	}
+	return res;
+}
+
+static enum bisect_error bisect_auto_next(struct bisect_terms *terms, const char *prefix)
+{
+	if (bisect_next_check(terms, NULL)) {
+		bisect_print_status(terms);
+		return BISECT_OK;
+	}
+
+	return bisect_next(terms, prefix);
+}
+
+static enum bisect_error bisect_start(struct bisect_terms *terms, const char **argv, int argc)
+{
+	int no_checkout = 0;
+	int first_parent_only = 0;
+	int i, has_double_dash = 0, must_write_terms = 0, bad_seen = 0;
+	int flags, pathspec_pos;
+	enum bisect_error res = BISECT_OK;
+	struct string_list revs = STRING_LIST_INIT_DUP;
+	struct string_list states = STRING_LIST_INIT_DUP;
+	struct strbuf start_head = STRBUF_INIT;
+	struct strbuf bisect_names = STRBUF_INIT;
+	struct object_id head_oid;
+	struct object_id oid;
+	const char *head;
+
+	if (is_bare_repository())
+		no_checkout = 1;
+
+	/*
+	 * Check for one bad and then some good revisions
+	 */
+	for (i = 0; i < argc; i++) {
+		if (!strcmp(argv[i], "--")) {
+			has_double_dash = 1;
+			break;
+		}
+	}
+
+	for (i = 0; i < argc; i++) {
+		const char *arg = argv[i];
+		if (!strcmp(argv[i], "--")) {
+			break;
+		} else if (!strcmp(arg, "--no-checkout")) {
+			no_checkout = 1;
+		} else if (!strcmp(arg, "--first-parent")) {
+			first_parent_only = 1;
+		} else if (!strcmp(arg, "--term-good") ||
+			 !strcmp(arg, "--term-old")) {
+			i++;
+			if (argc <= i)
+				return error(_("'' is not a valid term"));
+			must_write_terms = 1;
+			free((void *) terms->term_good);
+			terms->term_good = xstrdup(argv[i]);
+		} else if (skip_prefix(arg, "--term-good=", &arg) ||
+			   skip_prefix(arg, "--term-old=", &arg)) {
+			must_write_terms = 1;
+			free((void *) terms->term_good);
+			terms->term_good = xstrdup(arg);
+		} else if (!strcmp(arg, "--term-bad") ||
+			 !strcmp(arg, "--term-new")) {
+			i++;
+			if (argc <= i)
+				return error(_("'' is not a valid term"));
+			must_write_terms = 1;
+			free((void *) terms->term_bad);
+			terms->term_bad = xstrdup(argv[i]);
+		} else if (skip_prefix(arg, "--term-bad=", &arg) ||
+			   skip_prefix(arg, "--term-new=", &arg)) {
+			must_write_terms = 1;
+			free((void *) terms->term_bad);
+			terms->term_bad = xstrdup(arg);
+		} else if (starts_with(arg, "--")) {
+			return error(_("unrecognized option: '%s'"), arg);
+		} else if (!get_oidf(&oid, "%s^{commit}", arg)) {
+			string_list_append(&revs, oid_to_hex(&oid));
+		} else if (has_double_dash) {
+			die(_("'%s' does not appear to be a valid "
+			      "revision"), arg);
+		} else {
+			break;
+		}
+	}
+	pathspec_pos = i;
+
+	/*
+	 * The user ran "git bisect start <sha1> <sha1>", hence did not
+	 * explicitly specify the terms, but we are already starting to
+	 * set references named with the default terms, and won't be able
+	 * to change afterwards.
+	 */
+	if (revs.nr)
+		must_write_terms = 1;
+	for (i = 0; i < revs.nr; i++) {
+		if (bad_seen) {
+			string_list_append(&states, terms->term_good);
+		} else {
+			bad_seen = 1;
+			string_list_append(&states, terms->term_bad);
+		}
+	}
+
+	/*
+	 * Verify HEAD
+	 */
+	head = resolve_ref_unsafe("HEAD", 0, &head_oid, &flags);
+	if (!head)
+		if (get_oid("HEAD", &head_oid))
+			return error(_("bad HEAD - I need a HEAD"));
+
+	/*
+	 * Check if we are bisecting
+	 */
+	if (!is_empty_or_missing_file(git_path_bisect_start())) {
+		/* Reset to the rev from where we started */
+		strbuf_read_file(&start_head, git_path_bisect_start(), 0);
+		strbuf_trim(&start_head);
+		if (!no_checkout) {
+			struct child_process cmd = CHILD_PROCESS_INIT;
+
+			cmd.git_cmd = 1;
+			strvec_pushl(&cmd.args, "checkout", start_head.buf,
+				     "--", NULL);
+			if (run_command(&cmd)) {
+				res = error(_("checking out '%s' failed."
+						 " Try 'git bisect start "
+						 "<valid-branch>'."),
+					       start_head.buf);
+				goto finish;
+			}
+		}
+	} else {
+		/* Get the rev from where we start. */
+		if (!get_oid(head, &head_oid) &&
+		    !starts_with(head, "refs/heads/")) {
+			strbuf_reset(&start_head);
+			strbuf_addstr(&start_head, oid_to_hex(&head_oid));
+		} else if (!get_oid(head, &head_oid) &&
+			   skip_prefix(head, "refs/heads/", &head)) {
+			/*
+			 * This error message should only be triggered by
+			 * cogito usage, and cogito users should understand
+			 * it relates to cg-seek.
+			 */
+			if (!is_empty_or_missing_file(git_path_head_name()))
+				return error(_("won't bisect on cg-seek'ed tree"));
+			strbuf_addstr(&start_head, head);
+		} else {
+			return error(_("bad HEAD - strange symbolic ref"));
+		}
+	}
+
+	/*
+	 * Get rid of any old bisect state.
+	 */
+	if (bisect_clean_state())
+		return BISECT_FAILED;
+
+	/*
+	 * Write new start state
+	 */
+	write_file(git_path_bisect_start(), "%s\n", start_head.buf);
+
+	if (first_parent_only)
+		write_file(git_path_bisect_first_parent(), "\n");
+
+	if (no_checkout) {
+		if (get_oid(start_head.buf, &oid) < 0) {
+			res = error(_("invalid ref: '%s'"), start_head.buf);
+			goto finish;
+		}
+		if (update_ref(NULL, "BISECT_HEAD", &oid, NULL, 0,
+			       UPDATE_REFS_MSG_ON_ERR)) {
+			res = BISECT_FAILED;
+			goto finish;
+		}
+	}
+
+	if (pathspec_pos < argc - 1)
+		sq_quote_argv(&bisect_names, argv + pathspec_pos);
+	write_file(git_path_bisect_names(), "%s\n", bisect_names.buf);
+
+	for (i = 0; i < states.nr; i++)
+		if (bisect_write(states.items[i].string,
+				 revs.items[i].string, terms, 1)) {
+			res = BISECT_FAILED;
+			goto finish;
+		}
+
+	if (must_write_terms && write_terms(terms->term_bad,
+					    terms->term_good)) {
+		res = BISECT_FAILED;
+		goto finish;
+	}
+
+	res = bisect_append_log_quoted(argv);
+	if (res)
+		res = BISECT_FAILED;
+
+finish:
+	string_list_clear(&revs, 0);
+	string_list_clear(&states, 0);
+	strbuf_release(&start_head);
+	strbuf_release(&bisect_names);
+	if (res)
+		return res;
+
+	res = bisect_auto_next(terms, NULL);
+	if (!is_bisect_success(res))
+		bisect_clean_state();
+	return res;
+}
+
+static inline int file_is_not_empty(const char *path)
+{
+	return !is_empty_or_missing_file(path);
+}
+
+static int bisect_autostart(struct bisect_terms *terms)
+{
+	int res;
+	const char *yesno;
+
+	if (file_is_not_empty(git_path_bisect_start()))
+		return 0;
+
+	fprintf_ln(stderr, _("You need to start by \"git bisect "
+			  "start\"\n"));
+
+	if (!isatty(STDIN_FILENO))
+		return -1;
+
+	/*
+	 * TRANSLATORS: Make sure to include [Y] and [n] in your
+	 * translation. The program will only accept English input
+	 * at this point.
+	 */
+	yesno = git_prompt(_("Do you want me to do it for you "
+			     "[Y/n]? "), PROMPT_ECHO);
+	res = tolower(*yesno) == 'n' ?
+		-1 : bisect_start(terms, empty_strvec, 0);
+
+	return res;
+}
+
+static enum bisect_error bisect_state(struct bisect_terms *terms, const char **argv,
+				      int argc)
+{
+	const char *state;
+	int i, verify_expected = 1;
+	struct object_id oid, expected;
+	struct strbuf buf = STRBUF_INIT;
+	struct oid_array revs = OID_ARRAY_INIT;
+
+	if (!argc)
+		return error(_("Please call `--bisect-state` with at least one argument"));
+
+	if (bisect_autostart(terms))
+		return BISECT_FAILED;
+
+	state = argv[0];
+	if (check_and_set_terms(terms, state) ||
+	    !one_of(state, terms->term_good, terms->term_bad, "skip", NULL))
+		return BISECT_FAILED;
+
+	argv++;
+	argc--;
+	if (argc > 1 && !strcmp(state, terms->term_bad))
+		return error(_("'git bisect %s' can take only one argument."), terms->term_bad);
+
+	if (argc == 0) {
+		const char *head = "BISECT_HEAD";
+		enum get_oid_result res_head = get_oid(head, &oid);
+
+		if (res_head == MISSING_OBJECT) {
+			head = "HEAD";
+			res_head = get_oid(head, &oid);
+		}
+
+		if (res_head)
+			error(_("Bad rev input: %s"), head);
+		oid_array_append(&revs, &oid);
+	}
+
+	/*
+	 * All input revs must be checked before executing bisect_write()
+	 * to discard junk revs.
+	 */
+
+	for (; argc; argc--, argv++) {
+		struct commit *commit;
+
+		if (get_oid(*argv, &oid)){
+			error(_("Bad rev input: %s"), *argv);
+			oid_array_clear(&revs);
+			return BISECT_FAILED;
+		}
+
+		commit = lookup_commit_reference(the_repository, &oid);
+		if (!commit)
+			die(_("Bad rev input (not a commit): %s"), *argv);
+
+		oid_array_append(&revs, &commit->object.oid);
+	}
+
+	if (strbuf_read_file(&buf, git_path_bisect_expected_rev(), 0) < the_hash_algo->hexsz ||
+	    get_oid_hex(buf.buf, &expected) < 0)
+		verify_expected = 0; /* Ignore invalid file contents */
+	strbuf_release(&buf);
+
+	for (i = 0; i < revs.nr; i++) {
+		if (bisect_write(state, oid_to_hex(&revs.oid[i]), terms, 0)) {
+			oid_array_clear(&revs);
+			return BISECT_FAILED;
+		}
+		if (verify_expected && !oideq(&revs.oid[i], &expected)) {
+			unlink_or_warn(git_path_bisect_ancestors_ok());
+			unlink_or_warn(git_path_bisect_expected_rev());
+			verify_expected = 0;
+		}
+	}
+
+	oid_array_clear(&revs);
+	return bisect_auto_next(terms, NULL);
+}
+
+static enum bisect_error bisect_log(void)
+{
+	int fd, status;
+	const char* filename = git_path_bisect_log();
+
+	if (is_empty_or_missing_file(filename))
+		return error(_("We are not bisecting."));
+
+	fd = open(filename, O_RDONLY);
+	if (fd < 0)
+		return BISECT_FAILED;
+
+	status = copy_fd(fd, STDOUT_FILENO);
+	close(fd);
+	return status ? BISECT_FAILED : BISECT_OK;
+}
+
+static int process_replay_line(struct bisect_terms *terms, struct strbuf *line)
+{
+	const char *p = line->buf + strspn(line->buf, " \t");
+	char *word_end, *rev;
+
+	if ((!skip_prefix(p, "git bisect", &p) &&
+	!skip_prefix(p, "git-bisect", &p)) || !isspace(*p))
+		return 0;
+	p += strspn(p, " \t");
+
+	word_end = (char *)p + strcspn(p, " \t");
+	rev = word_end + strspn(word_end, " \t");
+	*word_end = '\0'; /* NUL-terminate the word */
+
+	get_terms(terms);
+	if (check_and_set_terms(terms, p))
+		return -1;
+
+	if (!strcmp(p, "start")) {
+		struct strvec argv = STRVEC_INIT;
+		int res;
+		sq_dequote_to_strvec(rev, &argv);
+		res = bisect_start(terms, argv.v, argv.nr);
+		strvec_clear(&argv);
+		return res;
+	}
+
+	if (one_of(p, terms->term_good,
+	   terms->term_bad, "skip", NULL))
+		return bisect_write(p, rev, terms, 0);
+
+	if (!strcmp(p, "terms")) {
+		struct strvec argv = STRVEC_INIT;
+		int res;
+		sq_dequote_to_strvec(rev, &argv);
+		res = bisect_terms(terms, argv.nr == 1 ? argv.v[0] : NULL);
+		strvec_clear(&argv);
+		return res;
+	}
+	error(_("'%s'?? what are you talking about?"), p);
+
+	return -1;
+}
+
+static enum bisect_error bisect_replay(struct bisect_terms *terms, const char *filename)
+{
+	FILE *fp = NULL;
+	enum bisect_error res = BISECT_OK;
+	struct strbuf line = STRBUF_INIT;
+
+	if (is_empty_or_missing_file(filename))
+		return error(_("cannot read file '%s' for replaying"), filename);
+
+	if (bisect_reset(NULL))
+		return BISECT_FAILED;
+
+	fp = fopen(filename, "r");
+	if (!fp)
+		return BISECT_FAILED;
+
+	while ((strbuf_getline(&line, fp) != EOF) && !res)
+		res = process_replay_line(terms, &line);
+
+	strbuf_release(&line);
+	fclose(fp);
+
+	if (res)
+		return BISECT_FAILED;
+
+	return bisect_auto_next(terms, NULL);
+}
+
+static enum bisect_error bisect_skip(struct bisect_terms *terms, const char **argv, int argc)
+{
+	int i;
+	enum bisect_error res;
+	struct strvec argv_state = STRVEC_INIT;
+
+	strvec_push(&argv_state, "skip");
+
+	for (i = 0; i < argc; i++) {
+		const char *dotdot = strstr(argv[i], "..");
+
+		if (dotdot) {
+			struct rev_info revs;
+			struct commit *commit;
+
+			init_revisions(&revs, NULL);
+			setup_revisions(2, argv + i - 1, &revs, NULL);
+
+			if (prepare_revision_walk(&revs))
+				die(_("revision walk setup failed\n"));
+			while ((commit = get_revision(&revs)) != NULL)
+				strvec_push(&argv_state,
+						oid_to_hex(&commit->object.oid));
+
+			reset_revision_walk();
+			release_revisions(&revs);
+		} else {
+			strvec_push(&argv_state, argv[i]);
+		}
+	}
+	res = bisect_state(terms, argv_state.v, argv_state.nr);
+
+	strvec_clear(&argv_state);
+	return res;
+}
+
+static int bisect_visualize(struct bisect_terms *terms, const char **argv, int argc)
+{
+	struct child_process cmd = CHILD_PROCESS_INIT;
+	struct strbuf sb = STRBUF_INIT;
+
+	if (bisect_next_check(terms, NULL) != 0)
+		return BISECT_FAILED;
+
+	cmd.no_stdin = 1;
+	if (!argc) {
+		if ((getenv("DISPLAY") || getenv("SESSIONNAME") || getenv("MSYSTEM") ||
+		     getenv("SECURITYSESSIONID")) && exists_in_PATH("gitk")) {
+			strvec_push(&cmd.args, "gitk");
+		} else {
+			strvec_push(&cmd.args, "log");
+			cmd.git_cmd = 1;
+		}
+	} else {
+		if (argv[0][0] == '-') {
+			strvec_push(&cmd.args, "log");
+			cmd.git_cmd = 1;
+		} else if (strcmp(argv[0], "tig") && !starts_with(argv[0], "git"))
+			cmd.git_cmd = 1;
+
+		strvec_pushv(&cmd.args, argv);
+	}
+
+	strvec_pushl(&cmd.args, "--bisect", "--", NULL);
+
+	strbuf_read_file(&sb, git_path_bisect_names(), 0);
+	sq_dequote_to_strvec(sb.buf, &cmd.args);
+	strbuf_release(&sb);
+
+	return run_command(&cmd);
+}
+
+static int get_first_good(const char *refname UNUSED,
+			  const struct object_id *oid,
+			  int flag UNUSED, void *cb_data)
+{
+	oidcpy(cb_data, oid);
+	return 1;
+}
+
+static int do_bisect_run(const char *command)
+{
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	printf(_("running %s\n"), command);
+	cmd.use_shell = 1;
+	strvec_push(&cmd.args, command);
+	return run_command(&cmd);
+}
+
+static int verify_good(const struct bisect_terms *terms, const char *command)
+{
+	int rc;
+	enum bisect_error res;
+	struct object_id good_rev;
+	struct object_id current_rev;
+	char *good_glob = xstrfmt("%s-*", terms->term_good);
+	int no_checkout = ref_exists("BISECT_HEAD");
+
+	for_each_glob_ref_in(get_first_good, good_glob, "refs/bisect/",
+			     &good_rev);
+	free(good_glob);
+
+	if (read_ref(no_checkout ? "BISECT_HEAD" : "HEAD", &current_rev))
+		return -1;
+
+	res = bisect_checkout(&good_rev, no_checkout);
+	if (res != BISECT_OK)
+		return -1;
+
+	rc = do_bisect_run(command);
+
+	res = bisect_checkout(&current_rev, no_checkout);
+	if (res != BISECT_OK)
+		return -1;
+
+	return rc;
+}
+
+static int bisect_run(struct bisect_terms *terms, const char **argv, int argc)
+{
+	int res = BISECT_OK;
+	struct strbuf command = STRBUF_INIT;
+	const char *new_state;
+	int temporary_stdout_fd, saved_stdout;
+	int is_first_run = 1;
+
+	if (bisect_next_check(terms, NULL))
+		return BISECT_FAILED;
+
+	if (!argc) {
+		error(_("bisect run failed: no command provided."));
+		return BISECT_FAILED;
+	}
+
+	sq_quote_argv(&command, argv);
+	strbuf_ltrim(&command);
+	while (1) {
+		res = do_bisect_run(command.buf);
+
+		/*
+		 * Exit code 126 and 127 can either come from the shell
+		 * if it was unable to execute or even find the script,
+		 * or from the script itself.  Check with a known-good
+		 * revision to avoid trashing the bisect run due to a
+		 * missing or non-executable script.
+		 */
+		if (is_first_run && (res == 126 || res == 127)) {
+			int rc = verify_good(terms, command.buf);
+			is_first_run = 0;
+			if (rc < 0 || 128 <= rc) {
+				error(_("unable to verify %s on good"
+					" revision"), command.buf);
+				res = BISECT_FAILED;
+				break;
+			}
+			if (rc == res) {
+				error(_("bogus exit code %d for good revision"),
+				      rc);
+				res = BISECT_FAILED;
+				break;
+			}
+		}
+
+		if (res < 0 || 128 <= res) {
+			error(_("bisect run failed: exit code %d from"
+				" %s is < 0 or >= 128"), res, command.buf);
+			break;
+		}
+
+		if (res == 125)
+			new_state = "skip";
+		else if (!res)
+			new_state = terms->term_good;
+		else
+			new_state = terms->term_bad;
+
+		temporary_stdout_fd = open(git_path_bisect_run(), O_CREAT | O_WRONLY | O_TRUNC, 0666);
+
+		if (temporary_stdout_fd < 0) {
+			res = error_errno(_("cannot open file '%s' for writing"), git_path_bisect_run());
+			break;
+		}
+
+		fflush(stdout);
+		saved_stdout = dup(1);
+		dup2(temporary_stdout_fd, 1);
+
+		res = bisect_state(terms, &new_state, 1);
+
+		fflush(stdout);
+		dup2(saved_stdout, 1);
+		close(saved_stdout);
+		close(temporary_stdout_fd);
+
+		print_file_to_stdout(git_path_bisect_run());
+
+		if (res == BISECT_ONLY_SKIPPED_LEFT)
+			error(_("bisect run cannot continue any more"));
+		else if (res == BISECT_INTERNAL_SUCCESS_MERGE_BASE) {
+			puts(_("bisect run success"));
+			res = BISECT_OK;
+		} else if (res == BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND) {
+			puts(_("bisect found first bad commit"));
+			res = BISECT_OK;
+		} else if (res) {
+			error(_("bisect run failed: 'bisect-state %s'"
+				" exited with error code %d"), new_state, res);
+		} else {
+			continue;
+		}
+		break;
+	}
+
+	strbuf_release(&command);
+	return res;
+}
+
+static int cmd_bisect__reset(int argc, const char **argv, const char *prefix UNUSED)
+{
+	if (argc > 1)
+		return error(_("'%s' requires either no argument or a commit"),
+			     "git bisect reset");
+	return bisect_reset(argc ? argv[0] : NULL);
+}
+
+static int cmd_bisect__terms(int argc, const char **argv, const char *prefix UNUSED)
+{
+	int res;
+	struct bisect_terms terms = { 0 };
+
+	if (argc > 1)
+		return error(_("'%s' requires 0 or 1 argument"),
+			     "git bisect terms");
+	res = bisect_terms(&terms, argc == 1 ? argv[0] : NULL);
+	free_terms(&terms);
+	return res;
+}
+
+static int cmd_bisect__start(int argc, const char **argv, const char *prefix UNUSED)
+{
+	int res;
+	struct bisect_terms terms = { 0 };
+
+	set_terms(&terms, "bad", "good");
+	res = bisect_start(&terms, argv, argc);
+	free_terms(&terms);
+	return res;
+}
+
+static int cmd_bisect__next(int argc, const char **argv UNUSED, const char *prefix)
+{
+	int res;
+	struct bisect_terms terms = { 0 };
+
+	if (argc)
+		return error(_("'%s' requires 0 arguments"),
+			     "git bisect next");
+	get_terms(&terms);
+	res = bisect_next(&terms, prefix);
+	free_terms(&terms);
+	return res;
+}
+
+static int cmd_bisect__log(int argc UNUSED, const char **argv UNUSED, const char *prefix UNUSED)
+{
+	return bisect_log();
+}
+
+static int cmd_bisect__replay(int argc, const char **argv, const char *prefix UNUSED)
+{
+	int res;
+	struct bisect_terms terms = { 0 };
+
+	if (argc != 1)
+		return error(_("no logfile given"));
+	set_terms(&terms, "bad", "good");
+	res = bisect_replay(&terms, argv[0]);
+	free_terms(&terms);
+	return res;
+}
+
+static int cmd_bisect__skip(int argc, const char **argv, const char *prefix UNUSED)
+{
+	int res;
+	struct bisect_terms terms = { 0 };
+
+	set_terms(&terms, "bad", "good");
+	get_terms(&terms);
+	res = bisect_skip(&terms, argv, argc);
+	free_terms(&terms);
+	return res;
+}
+
+static int cmd_bisect__visualize(int argc, const char **argv, const char *prefix UNUSED)
+{
+	int res;
+	struct bisect_terms terms = { 0 };
+
+	get_terms(&terms);
+	res = bisect_visualize(&terms, argv, argc);
+	free_terms(&terms);
+	return res;
+}
+
+static int cmd_bisect__run(int argc, const char **argv, const char *prefix UNUSED)
+{
+	int res;
+	struct bisect_terms terms = { 0 };
+
+	if (!argc)
+		return error(_("'%s' failed: no command provided."), "git bisect run");
+	get_terms(&terms);
+	res = bisect_run(&terms, argv, argc);
+	free_terms(&terms);
+	return res;
+}
+
+int cmd_bisect(int argc, const char **argv, const char *prefix)
+{
+	int res = 0;
+	parse_opt_subcommand_fn *fn = NULL;
+	struct option options[] = {
+		OPT_SUBCOMMAND("reset", &fn, cmd_bisect__reset),
+		OPT_SUBCOMMAND("terms", &fn, cmd_bisect__terms),
+		OPT_SUBCOMMAND("start", &fn, cmd_bisect__start),
+		OPT_SUBCOMMAND("next", &fn, cmd_bisect__next),
+		OPT_SUBCOMMAND("log", &fn, cmd_bisect__log),
+		OPT_SUBCOMMAND("replay", &fn, cmd_bisect__replay),
+		OPT_SUBCOMMAND("skip", &fn, cmd_bisect__skip),
+		OPT_SUBCOMMAND("visualize", &fn, cmd_bisect__visualize),
+		OPT_SUBCOMMAND("view", &fn, cmd_bisect__visualize),
+		OPT_SUBCOMMAND("run", &fn, cmd_bisect__run),
+		OPT_END()
+	};
+	argc = parse_options(argc, argv, prefix, options, git_bisect_usage,
+			     PARSE_OPT_SUBCOMMAND_OPTIONAL);
+
+	if (!fn) {
+		struct bisect_terms terms = { 0 };
+
+		if (!argc)
+			usage_msg_opt(_("need a command"), git_bisect_usage, options);
+
+		set_terms(&terms, "bad", "good");
+		get_terms(&terms);
+		if (check_and_set_terms(&terms, argv[0]))
+			usage_msg_optf(_("unknown command: '%s'"), git_bisect_usage,
+				       options, argv[0]);
+		res = bisect_state(&terms, argv, argc);
+		free_terms(&terms);
+	} else {
+		argc--;
+		argv++;
+		res = fn(argc, argv, prefix);
+	}
+
+	/*
+	 * Handle early success
+	 * From check_merge_bases > check_good_are_ancestors_of_bad > bisect_next_all
+	 */
+	if ((res == BISECT_INTERNAL_SUCCESS_MERGE_BASE) || (res == BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND))
+		res = BISECT_OK;
+
+	return -res;
+}