[pjtr]

purge is a third-party extension; it removes untracked files as you wrote.

But ~purge~ prune is also a command of the evolve extension, that is conceptually similar to strip, as GP wrote.

[quleap]

evolve doesn't have a purge command. It has a prune command.

purge is not a third party extension. It is distributed along with Mercurial.

[pjtr]

You are correct, thanks.