since ln was not using the -h it was following the target symlink
destination and deciding it was a destination directory. madness
ensued.
also test cleanup and more output and change linkables to use sets
will help with introducing and removing features, since the Cask
definitions move with every `brew update` and track master but the code
to handle them requires an explicit release and a `brew upgrade brew-cask`
relates to #179
`md5`, `sha1`, `sha256` all take a hexdigest string, e.g:
sha1 'f645e9da45a621415a07a7492c45923b1a1fd4d4'
`no_checksum` takes no argument, and indicates there is no checksum
for this cask. This is *not recommended*, and should only be used for
casks that have no versioned downloads.
`brew cask install` will complain if there is no sum provided (unless
`no_checksum` has been invoked), or if the sums do not match. It will
provide the computed checksum so the cask can be easily amended.
Adapted from @passcod's work in 82cc199ae6bbb1e98950e71a0573ab48e6a641ee
phinze
Paul Hinze