Simplify main interpreter

No need to interpret "multiple files in sequence".  Just execute the
one file given.

main.c

@@ -74,8 +74,8 @@ void interpret(machine_t *cpu, node_t *ast, size_t num)
 void usage(const char *name, FILE *fp)
 {
   fprintf(fp,
-          "Usage: %s [FILE]...\n\tExecutes FILES sequentially on the "
+          "Usage: %s [FILE]...\n\tInterprets FILE as a brainfuck program"
-          "same machine\n",
+          "\n",
           name);
 }
 
@@ -87,16 +87,12 @@ int main(int argc, char *argv[])
     return 1;
   }
 
-  char *filepath = NULL, *file_data = NULL;
+  int ret        = 0;
+  char *filepath = argv[1], *file_data = NULL;
   buffer_t *buffer   = NULL;
   struct PResult res = {0};
-
   machine_t machine  = {0};
 
-  for (int i = 1; i < argc; ++i)
-  {
-    filepath = argv[i];
-
   FILE *handle = fopen(filepath, "r");
 #ifdef DEBUG
   printf("[DEBUG]: Attempting to open file handle to %s\n", filepath);
@@ -104,7 +100,8 @@ int main(int argc, char *argv[])
   if (!handle)
   {
     fprintf(stderr, "ERROR: Could not open \"%s\"\n", filepath);
-      goto error;
+    ret = 1;
+    goto end;
   }
   file_data = fread_all(handle);
   fclose(handle);
@@ -120,7 +117,8 @@ int main(int argc, char *argv[])
   if (res.nodes == NULL)
   {
     fputs("Exiting early...\n", stderr);
-      goto error;
+    ret = 1;
+    goto end;
   }
 
 #ifdef DEBUG
@@ -140,17 +138,14 @@ int main(int argc, char *argv[])
       printf("\n\t");
     printf("%d    ", machine.memory[i]);
   }
+  printf("\n");
 #endif
-
+end:
-    free(res.nodes);
-    free(buffer);
-    free(file_data);
-  }
-  return 0;
-error:
-  if (buffer)
-    free(buffer);
   if (res.nodes)
     free(res.nodes);
-  return 1;
+  if (buffer)
+    free(buffer);
+  if (file_data)
+    free(file_data);
+  return ret;
 }