Refactor: Replace deferred code in yank commands with functions

[sandr01d]

Check list

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

Description

Many commands allow copying the commit hash or stash name of the current selection to the clipboard. We previously used deferred code to do so. This PR replaces the deferred code and binds these commands to functions instead.

Note

This PR belongs to #326 and resulted from discussions in #324.

Type of change

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

Test environment

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

[sandr01d]

Changes have been merged with #326