Command to edit .gitattributes

How would you feel about adding a command to more quickly add new items to git-crypt?
##### For example:

`git-crypt add foobar.txt` (or alternatively: `git-crypt encrypt foobar.txt`)
would be like running
`echo "foobar.txt filter=git-crypt diff=git-crypt" >> .gitattributes`

The aim here is for a simpler way to use `git-crypt` with less chance to screw up the syntax when adding new filters to `.gitattributes`