Merge branch 'js/gpg-errors'

[git.git] / builtin / bisect.c

#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_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, int argc,
                                      const char **argv)
{
        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)) {
                        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, 0, empty_strvec);

        return res;
}

static enum bisect_error bisect_state(struct bisect_terms *terms, int argc,
                                      const char **argv)
{
        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.nr, argv.v);
                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, int argc,
                                     const char **argv)
{
        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.nr, argv_state.v);

        strvec_clear(&argv_state);
        return res;
}

static int bisect_visualize(struct bisect_terms *terms, int argc,
                            const char **argv)
{
        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, int argc, const char **argv)
{
        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, 1, &new_state);

                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: 'git bisect %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, argc, argv);
        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, argc, argv);
        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, argc, argv);
        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, argc, argv);
        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, argc, argv);
                free_terms(&terms);
        } else {
                argc--;
                argv++;
                res = fn(argc, argv, prefix);
        }

        return is_bisect_success(res) ? 0 : -res;
}