feat(builtin.git_diff): new picker for diff hunks

[antonk52]

Description

This PR adds a picker for git diff hunks. The new picker may seem similar to git_status picker at first. However, it allows to view multiple hunks in a single file as separate entries; when a hunk is selected it jumps the cursor to the changes line instead of a first line of a file. You can also supply additinal arguments such as --ignore-all-space which can make hunks seem even more granular and easier to review when navigating via telescope. I have been testing this picker in my configuration for the past few months and think that other telescope users will find this useful.

I understand that at the time of first publishing this PR is in a pretty raw shape as it requires documentation updates and is currently using vim.fn.systemlist instead of an entry maker as entries cannot be inferred from a single line of output. I could not figure out a way to make the way the git diff output is parsed to work similar to how other pickers work. I if you think this is a welcome change I am happy to make appropriate changes to get this PR to a mergeable state.

Demo:

Screen.Recording.2024-05-22.at.01.36.07.mov

Look forward to see what you think about this feature.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

• Has hunks
  • Make changes in a git repository
  • run :Teelscope git_diff
  • expect to see a picker with diff hunks (multiple entries for single file with multiple hunks)
  • when an entry is selected it jumps to changed lines
• Clean git repositry
  • run :Teelscope git_diff
  • no picker, error message ""

Configuration:

• Neovim version (nvim --version): v0.10
• Operating system and version: macos 14.4

Checklist:

• My code follows the style guidelines of this project (stylua)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (lua annotations)

[jamestrew]

I'm sorry but we're not really accepting any new pickers at the moment. We're kinda struggling with maintaining all the ones we already have. See #1228

I would recommend packaging this as an extension to telescope though. See https://github.com/nvim-telescope/telescope.nvim/blob/c2ce039188e22288449e43b77710036e69a45a70/developers.md#bundling-as-extension

[nishantpillai5]

@antonk52 Would love this as an extension