bisect--helper: `bisect_autostart` shell function in C

Reimplement the `bisect_autostart` shell function in C and add the
C implementation from `bisect_next()` which was previously left
uncovered. Also add a subcommand `--bisect-autostart` to
`git bisect--helper` be called from `bisect_state()` from
git-bisect.sh .

Using `--bisect-autostart` subcommand is a temporary measure to port
shell function to C so as to use the existing test suite. As more
functions are ported, this subcommand will be retired and will be called
by `bisect_state()`.

Mentored-by: Lars Schneider <larsxschneider@gmail.com>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 41 insertions, 22 deletions

diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
index 502bf187e3..1767916505 100644
--- a/builtin/bisect--helper.c
+++ b/builtin/bisect--helper.c
@@ -30,6 +30,7 @@ static const char * const git_bisect_helper_usage[] = {
 					      "[--no-checkout] [<bad> [<good>...]] [--] [<paths>...]"),
 	N_("git bisect--helper --bisect-next"),
 	N_("git bisect--helper --bisect-auto-next"),
+	N_("git bisect--helper --bisect-autostart"),
 	NULL
 };
 
@@ -38,6 +39,8 @@ struct bisect_terms {
 	const char *term_bad;
 };
 
+static int bisect_autostart(struct bisect_terms *terms);
+
 /*
  * Check whether the string `term` belongs to the set of strings
  * included in the variable arguments.
@@ -422,6 +425,7 @@ static int bisect_next(struct bisect_terms *terms, const char *prefix)
 {
 	int res, no_checkout;
 
+	bisect_autostart(terms);
 	/*
 	 * In case of mistaken revs or checkout error, or signals received,
 	 * "bisect_auto_next" below may exit or misbehave.
@@ -754,6 +758,32 @@ finish:
 	return retval || bisect_auto_next(terms, NULL);
 }
 
+static int bisect_autostart(struct bisect_terms *terms)
+{
+	if (is_empty_or_missing_file(git_path_bisect_start())) {
+		const char *yesno;
+		const char *argv[] = {NULL};
+		fprintf(stderr, _("You need to start by \"git bisect "
+				  "start\"\n"));
+
+		if (!isatty(0))
+			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);
+		if (starts_with(yesno, "n") || starts_with(yesno, "N"))
+			exit(0);
+
+		return bisect_start(terms, 0, argv, 0);
+	}
+	return 0;
+}
+
 int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 {
 	enum {
@@ -767,6 +797,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		BISECT_START,
 		BISECT_NEXT,
 		BISECT_AUTO_NEXT,
+		BISECT_AUTOSTART,
 	} cmdmode = 0;
 	int no_checkout = 0, res = 0;
 	struct option options[] = {
@@ -790,6 +821,8 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 			 N_("find the next bisection commit"), BISECT_NEXT),
 		OPT_CMDMODE(0, "bisect-auto-next", &cmdmode,
 			 N_("verify the next bisection state then find the next bisection state"), BISECT_AUTO_NEXT),
+		OPT_CMDMODE(0, "bisect-autostart", &cmdmode,
+			 N_("start the bisection if BISECT_START empty or missing"), BISECT_AUTOSTART),
 		OPT_BOOL(0, "no-checkout", &no_checkout,
 			 N_("update BISECT_HEAD instead of checking out the current commit")),
 		OPT_END()
@@ -862,6 +895,13 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		get_terms(&terms);
 		res = bisect_auto_next(&terms, prefix);
 		break;
+	case BISECT_AUTOSTART:
+		if (argc)
+			die(_("--bisect-autostart requires 0 arguments"));
+		terms.term_good = "good";
+		terms.term_bad = "bad";
+		res = bisect_autostart(&terms);
+		break;
 	default:
 		die("BUG: unknown subcommand '%d'", cmdmode);
 	}
diff --git a/git-bisect.sh b/git-bisect.sh
index d574c448e0..cd56551c78 100755
--- a/git-bisect.sh
+++ b/git-bisect.sh
@@ -49,27 +49,6 @@ bisect_head()
 	fi
 }
 
-bisect_autostart() {
-	test -s "$GIT_DIR/BISECT_START" || {
-		gettextln "You need to start by \"git bisect start\"" >&2
-		if test -t 0
-		then
-			# TRANSLATORS: Make sure to include [Y] and [n] in your
-			# translation. The program will only accept English input
-			# at this point.
-			gettext "Do you want me to do it for you [Y/n]? " >&2
-			read yesno
-			case "$yesno" in
-			[Nn]*)
-				exit ;;
-			esac
-			git bisect--helper --bisect-start
-		else
-			exit 1
-		fi
-	}
-}
-
 bisect_skip() {
 	all=''
 	for arg in "$@"
@@ -86,7 +65,7 @@ bisect_skip() {
 }
 
 bisect_state() {
-	bisect_autostart
+	git bisect--helper --bisect-autostart
 	state=$1
 	get_terms
 	git bisect--helper --check-and-set-terms $state $TERM_GOOD $TERM_BAD || exit