It's the reverse. Adding const here means "doCommand will not change the string passed in". Any callers that have a non-const `char*` can still pass it in normally, since converting from `char *` to `const char *` is always allowed, just not the reverse.

The rationale for this change was that a literal string is also const, so a line like:

    char *foo = "bar";

results in a compiler warning (at least with -Wall).