Re: [PATCH v16 Part II 4/8] bisect--helper: `check_and_set_terms` shell function in C

> Reimplement the `check_and_set_terms` shell function in C and add
> `check-and-set-terms` subcommand to `git bisect--helper` to call it from
> git-bisect.sh
> 
> Using `--check-and-set-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.
> 
> check_and_set_terms() sets and receives two global variables namely
> TERM_GOOD and TERM_BAD in the shell script. Luckily the file BISECT_TERMS
> also contains the value of those variables so its appropriate to evoke the
> method get_terms() after calling the subcommand so that it retrieves the
> value of TERM_GOOD and TERM_BAD from the file BISECT_TERMS. The two
> global variables are passed as arguments to the subcommand.
> 
> Mentored-by: Lars Schneider <larsxschneider@gmail.com>
> Mentored-by: Christian Couder <chriscool@tuxfamily.org>
> Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
> ---
>  builtin/bisect--helper.c | 41 ++++++++++++++++++++++++++++++++++++++++-
>  git-bisect.sh            | 36 ++++--------------------------------
>  2 files changed, 44 insertions(+), 33 deletions(-)
> 
> diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
> index 6295f53c850a8..65abf8a70c6d9 100644
> --- a/builtin/bisect--helper.c
> +++ b/builtin/bisect--helper.c
> @@ -20,6 +20,7 @@ static const char * const git_bisect_helper_usage[] = {
>  	N_("git bisect--helper --bisect-clean-state"),
>  	N_("git bisect--helper --bisect-reset [<commit>]"),
>  	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>"),
>  	NULL
>  };
>  
> @@ -234,6 +235,35 @@ static int bisect_write(const char *state, const char *rev,
>  	return retval;
>  }
>  
> +static int check_and_set_terms(struct bisect_terms *terms, const char *cmd)
> +{
> +	int has_term_file = !is_empty_or_missing_file(git_path_bisect_terms());
> +
> +	if (one_of(cmd, "skip", "start", "terms", NULL))
> +		return 0;
> +
> +	if (has_term_file && strcmp(cmd, terms->term_bad) &&
> +	    strcmp(cmd, terms->term_good))
> +		return error(_("Invalid command: you're currently in a "
> +				"%s/%s bisect"), terms->term_bad,
> +				terms->term_good);
> +
> +	if (!has_term_file) {
> +		if (one_of(cmd, "bad", "good", NULL)) {
> +			free_terms(terms);
> +			set_terms(terms, "bad", "good");
> +			return write_terms(terms->term_bad, terms->term_good);
> +		}
> +		else if (one_of(cmd, "new", "old", NULL)) {