by specifying the full path of the package file, ie:

$ xbps-bin install ../some/path/pkgfile.x86_64.xbps

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I see that you would have to have a default 'user installed' package repo for the system.

What I mean is, so when somebody installs a single package, it should cache it in some systemwide repo that's meant only for those kinds of installs.

That way a user can keep track of what he's installed that way.

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I realized this is useless because one can just create a repo using xbps-src:

mkdir ~/some_repo_dir

And put pkgs into the corresponding arch subdirs: i686/, x86_64/, noarch/

Then run xbps-src make-repoidx

Then those individual pkgs will be available for the user to install/remove, etc.

Yes, that's what I thought too... that's why I haven't implemented it.