[PATCH 05/26] bisect.c: libify `bisect_checkout` 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 `bisect_checkout()`.

Handle 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 | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/bisect.c b/bisect.c
index bb926f09d0..1f2f3201a3 100644
--- a/bisect.c
+++ b/bisect.c
@@ -710,7 +710,7 @@ static int is_expected_rev(const struct object_id *oid)
 static int bisect_checkout(const struct object_id *bisect_rev, int no_checkout)
 {
 	char bisect_rev_hex[GIT_MAX_HEXSZ + 1];
-
+	int res = 0;
 	memcpy(bisect_rev_hex, oid_to_hex(bisect_rev), GIT_SHA1_HEXSZ + 1);
 	update_ref(NULL, "BISECT_EXPECTED_REV", bisect_rev, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
 
@@ -719,14 +719,14 @@ static int bisect_checkout(const struct object_id *bisect_rev, int no_checkout)
 		update_ref(NULL, "BISECT_HEAD", bisect_rev, NULL, 0,
 			   UPDATE_REFS_DIE_ON_ERR);
 	} else {
-		int res;
 		res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
 		if (res)
-			exit(res);
+			return res > 0 ? -res : res;
 	}
 
 	argv_show_branch[1] = bisect_rev_hex;
-	return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
+	res = run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
+	return res > 0 ? -res : res;
 }
 
 static struct commit *get_commit_reference(const struct object_id *oid)
@@ -822,7 +822,7 @@ static void check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
 			handle_skipped_merge_base(mb);
 		} else {
 			printf(_("Bisecting: a merge base must be tested\n"));
-			exit(bisect_checkout(mb, no_checkout));
+			exit(-bisect_checkout(mb, no_checkout));
 		}
 	}
 
-- 
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