trap SIGINT to clean up the display

I missed this initially because my zsh config does this automatically
for badly-behaved programs like pipeline.

src/main.c

@@ -6,6 +6,7 @@
 #include <math.h>
 #include <ncurses.h>
 #include <readline/readline.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/wait.h>
@@ -200,6 +201,12 @@ int setup() {
  return 0;
 }
 
+void cleanup(int sig) {
+ printf("\n");
+ termput0("cd");
+ exit(0);
+}
+
 static struct option const long_options[] = {
  {"truncate", no_argument, NULL, 't'},
  {"help", no_argument, NULL, 'h'},
@@ -241,7 +248,10 @@ int main(int argc, char *const *argv) {
 
  setupterm(NULL, 1, NULL);
  rl_startup_hook = setup;
+ signal(SIGINT, cleanup);
  char *line = readline("pipeline> ");
+ // as far as I'm aware, we'll never reach this point because
+ // we always exit with Ctrl-C.
  free(line);
  return 0;
 }