[PATCH 04/26] bisect.c: libify `exit_if_skipped_commits` to `error_if_skipped...`

["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.
Modify `cmd_bisect_helper()` to handle these negative returns.

Turn `exit()` to `return` calls in `exit_if_skipped_commits()` and rename
the method to `error_if_skipped_commits()`.

Handle this return in dependant method `bisect_next_all()`.

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 | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/bisect.c b/bisect.c
index 487675c672..bb926f09d0 100644
--- a/bisect.c
+++ b/bisect.c
@@ -659,11 +659,11 @@ static void bisect_common(struct rev_info *revs)
 		mark_edges_uninteresting(revs, NULL);
 }
 
-static void exit_if_skipped_commits(struct commit_list *tried,
+static int error_if_skipped_commits(struct commit_list *tried,
 				    const struct object_id *bad)
 {
 	if (!tried)
-		return;
+		return 0;
 
 	printf("There are only 'skip'ped commits left to test.\n"
 	       "The first %s commit could be any of:\n", term_bad);
@@ -674,7 +674,13 @@ static void exit_if_skipped_commits(struct commit_list *tried,
 	if (bad)
 		printf("%s\n", oid_to_hex(bad));
 	printf(_("We cannot bisect more!\n"));
-	exit(2);
+
+	/*
+	 * We don't want to clean the bisection state
+	 * as we need to get back to where we started
+	 * by using `git bisect reset`.
+	 */
+	return -2;
 }
 
 static int is_expected_rev(const struct object_id *oid)
@@ -949,7 +955,7 @@ int bisect_next_all(const char *prefix, int no_checkout)
 {
 	struct rev_info revs;
 	struct commit_list *tried;
-	int reaches = 0, all = 0, nr, steps;
+	int reaches = 0, all = 0, nr, steps, res;
 	struct object_id *bisect_rev;
 	char *steps_msg;
 
@@ -972,8 +978,9 @@ int bisect_next_all(const char *prefix, int no_checkout)
 		 * We should exit here only if the "bad"
 		 * commit is also a "skip" commit.
 		 */
-		exit_if_skipped_commits(tried, NULL);
-
+		res = error_if_skipped_commits(tried, NULL);
+		if (res)
+			exit(-res);
 		printf(_("%s was both %s and %s\n"),
 		       oid_to_hex(current_bad_oid),
 		       term_good,
@@ -990,7 +997,9 @@ int bisect_next_all(const char *prefix, int no_checkout)
 	bisect_rev = &revs.commits->item->object.oid;
 
 	if (oideq(bisect_rev, current_bad_oid)) {
-		exit_if_skipped_commits(tried, current_bad_oid);
+		res = error_if_skipped_commits(tried, current_bad_oid);
+		if (res)
+			exit(-res);
 		printf("%s is the first %s commit\n", oid_to_hex(bisect_rev),
 			term_bad);
 		show_diff_tree(prefix, revs.commits->item);
-- 
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