Re: [PATCH v16 Part II 6/8] bisect--helper: `get_terms` & `bisect_terms` shell function in C

Reimplement the `get_terms` and `bisect_terms` shell function in C and
add `bisect-terms` subcommand to `git bisect--helper` to call it from
git-bisect.sh .

Using `--bisect-terms` subcommand is a temporary measure to port shell
function in C so as to use the existing test suite. As more functions
are ported, this subcommand will be retired but its implementation will
be called by some other methods.

Also use error() to report "no terms defined" and accordingly change the
test in t6030.

Mentored-by: Lars Schneider [off-list ref]
Mentored-by: Christian Couder [off-list ref]
Signed-off-by: Pranit Bauva <redacted>
---
 builtin/bisect--helper.c    | 69 +++++++++++++++++++++++++++++++++++++++++++--
 git-bisect.sh               | 35 ++---------------------
 t/t6030-bisect-porcelain.sh |  2 +-
 3 files changed, 70 insertions(+), 36 deletions(-)

diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
index 0f9c3e63821b8..ab0580ce0089a 100644
--- a/builtin/bisect--helper.c
+++ b/builtin/bisect--helper.c

@@ -23,6 +23,7 @@ static const char * const git_bisect_helper_usage[] = {
 	N_("git bisect--helper --bisect-write <state> <revision> <good_term> <bad_term> [<nolog>]"),
 	N_("git bisect--helper --bisect-check-and-set-terms <command> <good_term> <bad_term>"),
 	N_("git bisect--helper --bisect-next-check [<term>] <good_term> <bad_term>"),
+	N_("git bisect--helper --bisect-terms [--term-good | --term-old | --term-bad | --term-new]"),
 	NULL
 };
 

@@ -344,6 +345,62 @@ static int bisect_next_check(const struct bisect_terms *terms,
 	return retval;
 }
 
+static int get_terms(struct bisect_terms *terms)
+{
+	struct strbuf str = STRBUF_INIT;
+	FILE *fp = NULL;
+	int res = 0;
+
+	fp = fopen(git_path_bisect_terms(), "r");
+	if (!fp)
+		goto fail;
+
+	free_terms(terms);
+	strbuf_getline_lf(&str, fp);
+	terms->term_bad = strbuf_detach(&str, NULL);
+	strbuf_getline_lf(&str, fp);
+	terms->term_good = strbuf_detach(&str, NULL);
+	goto finish;
+
+fail:
+	res = -1;
+finish:
+	if (fp)
+		fclose(fp);
+	strbuf_release(&str);
+	return res;
+}
+
+static int bisect_terms(struct bisect_terms *terms, const char **argv, int argc)
+{
+	int i;
+
+	if (get_terms(terms))
+		return error(_("no terms defined"));
+
+	if (argc > 1)
+		return error(_("--bisect-term requires exactly one argument"));
+
+	if (argc == 0)
+		return !printf(_("Your current terms are %s for the old state\n"
+				 "and %s for the new state.\n"),
+				 terms->term_good, terms->term_bad);