Improve stash command

[vrom911]

• named stashing
• list of stashes
• show the diff of the particular stash
• clear stashes

We can work on polishing this command. Let me know what do you think about what could be included 🙂

[chshersh]

Ideally, I'd love to keep the current behavior: hit stash stashes and hit unstash unstashes. And those commands take an argument, then it's a named stash, like hit stash doc-fix. However, this means that we will need to implement separate commands, like hit stash-list, hit stash-clear. Alternatively, names can be passed as parameters and all commands will be nested. So two versions
In short:

Version 1

hit stash
hit stash temp-fix
hit unstash
hit unstash temp-fix
hit stash-list
hit stash-diff

Version 2

hit stash
hit stash --name temp-fix
hit stash list
hit stash diff [Possible arguments]
hit stash clear

What would be the most convenient interface, you think? Also, I'm not sure whether optparse-applicative allows implementing the second version.