You can only run hg remove
on files that are tracked. To remove tracked files that match the .hgignore
patterns, run this command
$ hg forget "set:hgignore() and not ignored()"
This uses a fileset to select the right files.
If you want to remove files that are already ignored by Mercurial (not tracked), then see the purge extension. That can be used to cleanup a working copy so that it looks like a fresh checkout.