bisect: sanity check on terms

This is currently only a defensive check since the only terms are bad/good and new/old, which pass it, but this is a preparation step for accepting user-supplied terms. Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: moy

git-bisect.sh

@@ -535,9 +535,42 @@ get_terms () {
 write_terms () {
 TERM_BAD=$1
 TERM_GOOD=$2
+if test "$TERM_BAD" = "$TERM_GOOD"
+then
+die "$(gettext "please use two different terms")"
+fi
+check_term_format "$TERM_BAD" bad
+check_term_format "$TERM_GOOD" good
 printf '%s\n%s\n' "$TERM_BAD" "$TERM_GOOD" >"$GIT_DIR/BISECT_TERMS"
 }
 
+check_term_format () {
+term=$1
+git check-ref-format refs/bisect/"$term" ||
+die "$(eval_gettext "'\$term' is not a valid term")"
+case "$term" in
+help|start|terms|skip|next|reset|visualize|replay|log|run)
+die "$(eval_gettext "can't use the builtin command '\$term' as a term")"
+;;
+bad|new)
+if test "$2" != bad
+then
+# In theory, nothing prevents swapping
+# completely good and bad, but this situation
+# could be confusing and hasn't been tested
+# enough. Forbid it for now.
+die "$(eval_gettext "can't change the meaning of term '\$term'")"
+fi
+;;
+good|old)
+if test "$2" != good
+then
+die "$(eval_gettext "can't change the meaning of term '\$term'")"
+fi
+;;
+esac
+}
+
 check_and_set_terms () {
 cmd="$1"
 case "$cmd" in