[PATCH 08/26] bisect.c: libify `handle_bad_merge_base` and its dependants

["Pranit Bauva via GitGitGadget" <gitgitgadget@gmail.com>]

From: Pranit Bauva <pranit.bauva@gmail.com>

Since we want to get rid of git-bisect.sh it would be necessary to
convert those exit() calls to return statements so that errors can be
reported.

Emulate try catch in C by converting `exit(<positive-value>)` to
`return <negetive-value>`. Follow POSIX conventions to return
<negative-value> to indicate error.

Turn `exit()` to `return` calls in `handle_bad_merge_base()`.

Handle/libify this return in dependant methods - `check_merge_bases()`.

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>
---
 bisect.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/bisect.c b/bisect.c
index 87db1cc4be..b1ea658a75 100644
--- a/bisect.c
+++ b/bisect.c
@@ -751,7 +751,7 @@ static struct commit **get_bad_and_good_commits(int *rev_nr)
 	return rev;
 }
 
-static void handle_bad_merge_base(void)
+static int handle_bad_merge_base(void)
 {
 	if (is_expected_rev(current_bad_oid)) {
 		char *bad_hex = oid_to_hex(current_bad_oid);
@@ -772,14 +772,14 @@ static void handle_bad_merge_base(void)
 				"between %s and [%s].\n"),
 				bad_hex, term_bad, term_good, bad_hex, good_hex);
 		}
-		exit(3);
+		return -3;
 	}
 
 	fprintf(stderr, _("Some %s revs are not ancestors of the %s rev.\n"
 		"git bisect cannot work properly in this case.\n"
 		"Maybe you mistook %s and %s revs?\n"),
 		term_good, term_bad, term_good, term_bad);
-	exit(1);
+	return -1;
 }
 
 static void handle_skipped_merge_base(const struct object_id *mb)
@@ -818,7 +818,8 @@ static int check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
 	for (; result; result = result->next) {
 		const struct object_id *mb = &result->item->object.oid;
 		if (oideq(mb, current_bad_oid)) {
-			handle_bad_merge_base();
+			res = handle_bad_merge_base();
+			break;
 		} else if (0 <= oid_array_lookup(&good_revs, mb)) {
 			continue;
 		} else if (0 <= oid_array_lookup(&skipped_revs, mb)) {
-- 
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