Hi

I was making some hooks to pacman to regenerate fish completions upon installing/updating packages. Regenerating all completions each time can be pointless, and in most cases we're interested in generating only few completions.

This can be done by getting this info from package manager and manually choose files to fish_update_completions. It is unfortunately distro-dependent and maybe needs some logic already existing in code (mapping manpage names into completion names for example).

My proposal is to implement this as an optional flag into script - for example by checking mod times of manpages and completions. I am willing to implement this change if accepted.