Support stashes in forgit::diff

[carlfriedrich]

Check list

• [x] I have performed a self-review of my code
• [x] I have commented my code in hard-to-understand areas
• [x] I have made corresponding changes to the documentation

Description

Git stashes are named stash@{x}, which contains the fzf placeholder {x}. In order to support passing stashes as arguments to forgit::diff, we have to prevent fzf from interpreting this substring by escaping the opening bracket.

Before:

After:

Type of change

• [x] Bug fix
• [ ] New feature
• [ ] Refactor
• [ ] Breaking change
• [ ] Documentation change

Test environment

• Shell
  • [x] bash
  • [x] zsh
  • [x] fish
• OS
  • [x] Linux
  • [ ] Mac OS X
  • [ ] Windows
  • [ ] Others:

[cjappl]

seems like a good extension to me! Assigning to @wfxr