bisect--helper: finish porting `bisect_start()` to C

Add the subcommand to `git bisect--helper` and call it from
git-bisect.sh.

With the conversion of `bisect_auto_next()` from shell to C in a
previous commit, `bisect_start()` can now be fully ported to C.

So let's complete the `--bisect-start` subcommand of
`git bisect--helper` so that it fully implements `bisect_start()`,
and let's use this subcommand in `git-bisect.sh` instead of
`bisect_start()`.

Note that the `eval` in the changed line of `git-bisect.sh` cannot be
dropped: it is necessary because the `rev` and the `tail`
variables may contain multiple, quoted arguments that need to be
passed to `bisect--helper` (without the quotes, naturally).

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>
Reviewed-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 27 insertions, 14 deletions

diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
index 64f16d5d92..0196ee144c 100644
--- a/builtin/bisect--helper.c
+++ b/builtin/bisect--helper.c
@@ -85,6 +85,19 @@ static int one_of(const char *term, ...)
 	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;
@@ -609,12 +622,13 @@ static enum bisect_error bisect_auto_next(struct bisect_terms *terms, const char
 	return bisect_next(terms, prefix);
 }
 
-static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
+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, res = 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;
@@ -754,14 +768,7 @@ static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
 	 * Get rid of any old bisect state.
 	 */
 	if (bisect_clean_state())
-		return -1;
-
-	/*
-	 * In case of mistaken revs or checkout error, or signals received,
-	 * "bisect_auto_next" below may exit or misbehave.
-	 * We have to trap this to be able to clean up using
-	 * "bisect_clean_state".
-	 */
+		return BISECT_FAILED;
 
 	/*
 	 * Write new start state
@@ -778,7 +785,7 @@ static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
 		}
 		if (update_ref(NULL, "BISECT_HEAD", &oid, NULL, 0,
 			       UPDATE_REFS_MSG_ON_ERR)) {
-			res = -1;
+			res = BISECT_FAILED;
 			goto finish;
 		}
 	}
@@ -790,25 +797,31 @@ static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
 	for (i = 0; i < states.nr; i++)
 		if (bisect_write(states.items[i].string,
 				 revs.items[i].string, terms, 1)) {
-			res = -1;
+			res = BISECT_FAILED;
 			goto finish;
 		}
 
 	if (must_write_terms && write_terms(terms->term_bad,
 					    terms->term_good)) {
-		res = -1;
+		res = BISECT_FAILED;
 		goto finish;
 	}
 
 	res = bisect_append_log_quoted(argv);
 	if (res)
-		res = -1;
+		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;
 }