Pass some file metadata to commands with familiar keywords

[mndvns]

Something similar to make's CURDIR and stuff.

Some ideas:

• $file as filename
• $path as full path
• $base as base name
• $ext as file extension

So for example in the lr.yml...

public: '@echo "$file just changed"'

Yeah. Something like that.

[mndvns]

Either steal the keywords from make or bash or node or somebody.

It should be familiar.