Add version pinning functionality

[dongyuzheng]

Why

I found myself needing this when I didn't want to update java8.

This PR resolves #108, resolves #93, resolves #90, resolves #72

Not included in this PR

Currently you can pin casks that are not installed. So you can pin asdasfsadasd

Usage

gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu --help
...

OPTIONS:
...
    If --pinned is passed, print all pinned apps

    If --pin CASK is passed, pin the current app version

    If --unpin CASK is passed, unpin the current app version

Example usage

gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu --pinned
java8
gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu --pin firefox
Pinned: firefox
gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu --pin firefox
Already pinned: firefox
gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu --pinned
java8
firefox
gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu --unpin firefox
Unpinned: firefox
gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu --unpin firefox
Not pinned: firefox
gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu --pinned
java8
gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu
==> Options
Include auto-update (-a): false
Include latest (-f): false
==> Updating Homebrew
Already up-to-date.
==> Finding outdated apps
       Cask                    Current                  Latest                A/U    Result
...
 8/19  java8                   1.8.0_192-b12,750e1c...  8.202.03,07_nov_2018       [ PINNED ]
...
gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu --unpin java8
Unpinned: java8
gary@v1020-wn-17-117:~/pg/homebrew-cask-upgrade (master)$ brew cu
==> Options
Include auto-update (-a): false
Include latest (-f): false
==> Updating Homebrew
Already up-to-date.
==> Finding outdated apps
       Cask                    Current                  Latest                A/U    Result
...
 8/19  java8                   1.8.0_192-b12,750e1c...  8.202.03,07_nov_2018       [OUTDATED]
...
==> Found outdated apps
     Cask   Current                                         Latest                A/U    Result
1/1  java8  1.8.0_192-b12,750e1c8617c5452694857ad95c3ee230  8.202.03,07_nov_2018       [OUTDATED]

Do you want to upgrade 1 app [y/N]? ^C

[ondrejfuhrer]

Please fix rubocop offenses: https://travis-ci.org/buo/homebrew-cask-upgrade/builds/482972228

[ondrejfuhrer]

Hey @dongyuzheng , thanks a lot for your contribution! It's nice that someone found a time to do that. Please do me a favour and change the description here so that instead of lust listing those issues change it to Resolves: #... so that when the PR is merged, those issues are automatically closed.

Thanks! 👍

[dongyuzheng]

Hi @ondrejfuhrer, does my latest commit give desired output for your case?

[ondrejfuhrer]

Everywhere we / Homebrew uses CASK, I don't see a reason why we should introduce new naming? I saw that in one of the versions you had used that, any particular reason why you decided to use different naming?

[dongyuzheng]

I saw that the code/documentation used app in some places, so I change them to app to be consistent. But I changed it to cask now.

[ondrejfuhrer]

Looks good to me 👍 Now it has to wait for @buo

[muescha]

i think the pinned file should be better in the ~/ folder. for example as ~/.brew-cu-pinned

[ondrejfuhrer]

@muescha Not sure if that would make any difference. Not even the Homebrew core is using a home folder for that and they are pinning it within Homebrew structure, so I don't see any important reason why would you do that.

Also if you would remove the tap it would leave those files on the home folder which is not very clean.

[yurikoles]

I think @ondrejfuhrer is right, there is --appdir option, but it still uses global Caskroom for apps.

[muescha]

ok - you are right, it should be the same as the homebrew core behaviour