bisect--helper: `bisect_clean_state` shell function in C

Reimplement `bisect_clean_state` shell function in C and add a
`bisect-clean-state` subcommand to `git bisect--helper` to call it from
git-bisect.sh .

Using `--bisect-clean-state` subcommand is a measure to port shell
function to 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 bisect_reset() and bisect_start().

Also introduce a function `mark_for_removal` to store the refs which
need to be removed while iterating through the refs.

Mentored-by: Lars Schneider <larsxschneider@gmail.com>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/bisect.h b/bisect.h
index acd12ef802..0ae63d4616 100644
--- a/bisect.h
+++ b/bisect.h
@@ -28,4 +28,6 @@ extern int estimate_bisect_steps(int all);
 
 extern void read_bisect_terms(const char **bad, const char **good);
 
+extern int bisect_clean_state(void);
+
 #endif