DRY up the `JUST_FILE` Regexp
DRY up the `JUST_FILE` Regexp

Now that we support dots at the beginning of `JUST_FILE` filenames.

alecjacobson/PathPicker,alecjacobson/PathPicker,alecjacobson/PathPicker,pallavagarwal07/PathPicker,facebook/PathPicker,Shenil/PathPicker,facebook/PathPicker,slackorama/PathPicker,Shenil/PathPicker,Shenil/PathPicker,slackorama/PathPicker,facebook/PathPicker,pallavagarwal07/PathPicker,pallavagarwal07/PathPicker,Shenil/PathPicker,alecjacobson/PathPicker,facebook/PathPicker,Shenil/PathPicker,pallavagarwal07/PathPicker,slackorama/PathPicker,alecjacobson/PathPicker,slackorama/PathPicker