Generalize string trunctation util function

Add an additional argument to let the client pass the possible end
chars.

app/src/util/str.h

@@ -104,7 +104,7 @@ char *
 sc_str_wrap_lines(const char *input, unsigned columns, unsigned indent);
 
 /**
- * Truncate the data after the first line
+ * Truncate the data after any of the characters from `endchars`
  *
  * An '\0' is always written at the end of the data, even if no newline
  * character is encountered.
@@ -112,6 +112,6 @@ sc_str_wrap_lines(const char *input, unsigned columns, unsigned indent);
  * Return the size of the resulting line.
  */
 size_t
-sc_str_truncate_first_line(char *data, size_t len);
+sc_str_truncate(char *data, size_t len, const char *endchars);
 
 #endif