feature request for crancache_remove

[bbolker]

I have two minor usability gripes with crancache_remove():

• the regex-matching feature is a little dangerous; I can't remember when, but I think I've accidentally removed packages this way in the past
• I have a hard time remembering that it's not remove_packages() (in parallel with update_packages(), install_packages()

Adding a remove_packages() function that did string-matching rather than regex-matching would preserve backward compatibility ...

[gaborcsardi]

If we had a remove_packages() that should remove the packages from the library and not from the cache. At least this is how the other replacement functions work.

We could have crancache_remove(..., fixed = TRUE) or something similar? A PR is welcome for this. :)