Re: [PATCH v7 06/13] bisect--helper: reimplement `bisect_next` and `bisect_auto_next` shell functions in C

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Sep 3, 2020, 09:48 UTC
Message-ID: <nycvar.QRO.7.76.6.2009030800000.56@tvgsbejvaqbjf.bet>
In-Reply-To: <20200831105043.97665-7-mirucam@gmail.com>

Hi Miriam,

On Mon, 31 Aug 2020, Miriam Rubio wrote:

Show 236 quoted lines

> From: Pranit Bauva <pranit.bauva@gmail.com>
>
> Reimplement the `bisect_next()` and the `bisect_auto_next()` shell functions
> in C and add the subcommands to `git bisect--helper` to call them from
> git-bisect.sh .
>
> bisect_auto_next() function returns an enum bisect_error type as whole
> `git bisect` can exit with an error code when bisect_next() does.
>
> Using `--bisect-next` and `--bisect-auto-next` subcommands is a
> temporary measure to port shell function to C so as to use the existing
> test suite. As more functions are ported, `--bisect-auto-next`
> subcommand will be retired and will be called by some other methods.
>
> Mentored-by: Lars Schneider <larsxschneider@gmail.com>
> Mentored-by: Christian Couder <chriscool@tuxfamily.org>
> Mentored-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
> Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
> Signed-off-by: Tanushree Tumane <tanushreetumane@gmail.com>
> Signed-off-by: Miriam Rubio <mirucam@gmail.com>
> ---
>  bisect.c                 |  11 ++-
>  builtin/bisect--helper.c | 180 ++++++++++++++++++++++++++++++++++++++-
>  git-bisect.sh            |  47 +---------
>  3 files changed, 190 insertions(+), 48 deletions(-)
>
> diff --git a/bisect.c b/bisect.c
> index c6aba2b9f2..f5b1368128 100644
> --- a/bisect.c
> +++ b/bisect.c
> @@ -988,8 +988,11 @@ void read_bisect_terms(const char **read_bad, const char **read_good)
>   * the bisection process finished successfully.
>   * In this case the calling function or command should not turn a
>   * BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND return code into an error or a non zero exit code.
> - * If no_checkout is non-zero, the bisection process does not
> - * checkout the trial commit but instead simply updates BISECT_HEAD.
> + *
> + * Checking BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND
> + * in bisect_helper::bisect_next() and only transforming it to 0 at
> + * the end of bisect_helper::cmd_bisect__helper() helps bypassing
> + * all the code related to finding a commit to test.
>   */
>  enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
>  {
> @@ -999,6 +1002,10 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
>  	enum bisect_error res = BISECT_OK;
>  	struct object_id *bisect_rev;
>  	char *steps_msg;
> +	/*
> +	 * If no_checkout is non-zero, the bisection process does not
> +	 * checkout the trial commit but instead simply updates BISECT_HEAD.
> +	 */
>  	int no_checkout = ref_exists("BISECT_HEAD");
>  	unsigned bisect_flags = 0;
>
> diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
> index f71e8e54d2..e29e86142a 100644
> --- a/builtin/bisect--helper.c
> +++ b/builtin/bisect--helper.c
> @@ -8,6 +8,7 @@
>  #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")
> @@ -29,10 +30,17 @@ static const char * const git_bisect_helper_usage[] = {
>  	N_("git bisect--helper --bisect-terms [--term-good | --term-old | --term-bad | --term-new]"),
>  	N_("git bisect--helper --bisect-start [--term-{old,good}=<term> --term-{new,bad}=<term>]"
>  					    " [--no-checkout] [--first-parent] [<bad> [<good>...]] [--] [<paths>...]"),
> +	N_("git bisect--helper --bisect-next"),
> +	N_("git bisect--helper --bisect-auto-next"),
>  	N_("git bisect--helper --bisect-autostart"),
>  	NULL
>  };
>
> +struct add_bisect_ref_data {
> +	struct rev_info *revs;
> +	unsigned int object_flags;
> +};
> +
>  struct bisect_terms {
>  	char *term_good;
>  	char *term_bad;
> @@ -56,6 +64,8 @@ static void set_terms(struct bisect_terms *terms, const char *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.
> @@ -80,7 +90,7 @@ static int write_in_file(const char *path, const char *mode, const char *format,
>  	FILE *fp = NULL;
>  	int res = 0;
>
> -	if (strcmp(mode, "w"))
> +	if (strcmp(mode, "w") && strcmp(mode, "a"))
>  		BUG("write-in-file does not support '%s' mode", mode);
>  	fp = fopen(path, mode);
>  	if (!fp)
> @@ -109,6 +119,18 @@ static int write_to_file(const char *path, const char *format, ...)
>  	return res;
>  }
>
> +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 check_term_format(const char *term, const char *orig_term)
>  {
>  	int res;
> @@ -451,6 +473,140 @@ static int bisect_append_log_quoted(const char **argv)
>  	return res;
>  }
>
> +static int add_bisect_ref(const char *refname, const struct object_id *oid,
> +			  int flags, 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);
> +	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;
> +
> +	bisect_autostart(terms);

We need to handle a negative value returned by `bisect_autostart()` by aborting, e.g. `return BISECT_FAILED;`.

Show 22 quoted lines

> +	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))
> +		return BISECT_OK;
> +
> +	return bisect_next(terms, prefix);

This returns an error when `bisect_next()` failed, which is different from what the shell script version did:

	git bisect--helper --bisect-next-check $TERM_GOOD $TERM_BAD && bisect_next || :

(note the trailing `|| :`, which will always return success).

I think this is a bug fix, though, so the change is good. But it probably deserves to be called out in the commit message.

Show 13 quoted lines

> +}
> +
>  static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
>  {
>  	int no_checkout = 0;
> @@ -699,7 +855,9 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
>  		BISECT_NEXT_CHECK,
>  		BISECT_TERMS,
>  		BISECT_START,
> -		BISECT_AUTOSTART,
> +		BISECT_NEXT,
> +		BISECT_AUTO_NEXT,
> +		BISECT_AUTOSTART

I am curious: what is the reason not to use a trailing comma, and what is the reason to force AUTOSTART to stay at the end (instead of appending the new modes, which strikes me as more natural)?

Show 109 quoted lines

>  	} cmdmode = 0;
>  	int res = 0, nolog = 0;
>  	struct option options[] = {
> @@ -723,6 +881,10 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
>  			 N_("print out the bisect terms"), BISECT_TERMS),
>  		OPT_CMDMODE(0, "bisect-start", &cmdmode,
>  			 N_("start the bisect session"), BISECT_START),
> +		OPT_CMDMODE(0, "bisect-next", &cmdmode,
> +			 N_("find the next bisection commit"), BISECT_NEXT),
> +		OPT_CMDMODE(0, "bisect-auto-next", &cmdmode,
> +			 N_("verify the next bisection state then checkout the next bisection commit"), BISECT_AUTO_NEXT),
>  		OPT_CMDMODE(0, "bisect-autostart", &cmdmode,
>  			 N_("start the bisection if it has not yet been started"), BISECT_AUTOSTART),
>  		OPT_BOOL(0, "no-log", &nolog,
> @@ -784,6 +946,18 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
>  		set_terms(&terms, "bad", "good");
>  		res = bisect_start(&terms, argv, argc);
>  		break;
> +	case BISECT_NEXT:
> +		if (argc)
> +			return error(_("--bisect-next requires 0 arguments"));
> +		get_terms(&terms);
> +		res = bisect_next(&terms, prefix);
> +		break;
> +	case BISECT_AUTO_NEXT:
> +		if (argc)
> +			return error(_("--bisect-auto-next requires 0 arguments"));
> +		get_terms(&terms);
> +		res = bisect_auto_next(&terms, prefix);
> +		break;
>  	case BISECT_AUTOSTART:
>  		if (argc)
>  			return error(_("--bisect-autostart does not accept arguments"));
> @@ -799,7 +973,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
>  	 * Handle early success
>  	 * From check_merge_bases > check_good_are_ancestors_of_bad > bisect_next_all
>  	 */
> -	if (res == BISECT_INTERNAL_SUCCESS_MERGE_BASE)
> +	if ((res == BISECT_INTERNAL_SUCCESS_MERGE_BASE) || (res == BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND))
>  		res = BISECT_OK;
>
>  	return -res;
> diff --git a/git-bisect.sh b/git-bisect.sh
> index 9ca583d964..59424f5b37 100755
> --- a/git-bisect.sh
> +++ b/git-bisect.sh
> @@ -65,8 +65,7 @@ bisect_start() {
>  	#
>  	# Check if we can proceed to the next bisect state.
>  	#
> -	get_terms
> -	bisect_auto_next
> +	git bisect--helper --bisect-auto-next || exit
>
>  	trap '-' 0
>  }
> @@ -119,45 +118,7 @@ bisect_state() {
>  	*)
>  		usage ;;
>  	esac
> -	bisect_auto_next
> -}
> -
> -bisect_auto_next() {
> -	git bisect--helper --bisect-next-check $TERM_GOOD $TERM_BAD && bisect_next || :
> -}
> -
> -bisect_next() {
> -	case "$#" in 0) ;; *) usage ;; esac
> -	git bisect--helper --bisect-autostart
> -	git bisect--helper --bisect-next-check $TERM_GOOD $TERM_BAD $TERM_GOOD|| exit
> -
> -	# Perform all bisection computation, display and checkout
> -	git bisect--helper --next-all
> -	res=$?
> -
> -	# Check if we should exit because bisection is finished
> -	if test $res -eq 10
> -	then
> -		bad_rev=$(git show-ref --hash --verify refs/bisect/$TERM_BAD)
> -		bad_commit=$(git show-branch $bad_rev)
> -		echo "# first $TERM_BAD commit: $bad_commit" >>"$GIT_DIR/BISECT_LOG"
> -		exit 0
> -	elif test $res -eq 2
> -	then
> -		echo "# only skipped commits left to test" >>"$GIT_DIR/BISECT_LOG"
> -		good_revs=$(git for-each-ref --format="%(objectname)" "refs/bisect/$TERM_GOOD-*")
> -		for skipped in $(git rev-list refs/bisect/$TERM_BAD --not $good_revs)
> -		do
> -			skipped_commit=$(git show-branch $skipped)
> -			echo "# possible first $TERM_BAD commit: $skipped_commit" >>"$GIT_DIR/BISECT_LOG"
> -		done
> -		exit $res
> -	fi
> -
> -	# Check for an error in the bisection process
> -	test $res -ne 0 && exit $res
> -
> -	return 0
> +	git bisect--helper --bisect-auto-next
>  }
>
>  bisect_visualize() {
> @@ -213,7 +174,7 @@ bisect_replay () {
>  		esac
>  	done <"$file"
>  	IFS="$oIFS"
> -	bisect_auto_next
> +	git bisect--helper --bisect-auto-next

We probably need to append `|| exit` here.

Thank you, Johannes

Show 16 quoted lines

>  }
>
>  bisect_run () {
> @@ -310,7 +271,7 @@ case "$#" in
>  		bisect_skip "$@" ;;
>  	next)
>  		# Not sure we want "next" at the UI level anymore.
> -		bisect_next "$@" ;;
> +		git bisect--helper --bisect-next "$@" || exit ;;
>  	visualize|view)
>  		bisect_visualize "$@" ;;
>  	reset)
> --
> 2.25.0
>
>