alot/utils/argparse: Add a new argparse validators infrastructure

This adds a new argparse.Action class validates input using a new
keyword argument that takes a validator function. This will allow us to
replace the use the type keyword as a validator, which is both more
correct, and frees up the type keyword to do what it's actually meant to
do, convert the input from one type to another.

It also adds 3 new validator functions that will be enabled in the next
commit. One that checks for a required file, one that checks for an
optional directory, and one that looks for a required file, fifo, or
block special device (/dev/null).

0 files changed, 0 insertions, 0 deletions