feat: Add aliases for git diff staged and cached

[hermitmaster]

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

Added aliases for git diff --staged and git diff --cached

Type of change

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

Test environment

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

Closes #174

[cjappl]

LGTM besides the small comment. Leaving it up to @wfxr if we want to take the change or not.

Thanks for the contribution :)

[wfxr]

Well, why not just add two lines in your shell's config? I think it's a more elegant way.

alias gdca='gd --cached'
alias gds='gd --staged'

And more aliases like alias gdh='gd HEAD' etc.