I want to mirror a large site.  I already have a mirror
started with another program; the file structure is
identical to what HTTrack would use, only there is no
hts-cache, of course.

If I use HTTrack with this, will HTTrack "detect" the
already-existing files when it goes to download a file, or
will it just blindly overwrite the already-existing
identical files?  TIA.