--skip-phase prerm/postrm doesn't work

[moben]

I think it only affects the exheres that is to be installed, not the one that is to be uninstalled.

This behavior doesn't make sense at all, because those phases are only run on uninstall.

but then, those only make sense on uninstall/reinstall/update not new install. But some other phases only apply for the latter, so maybe that's alright

[ciaranm]

This one's a fairly easy but tedious patch that anyone can do: grep for want_phase, and add that logic into UninstallAction? (it's only there for InstallAction? and FetchAction?).