feat(commit): add AI-generated commit message support. (v2)

[Blankeos]

PR Description

This is a simplified version of this PR #5389. I removed the OpenAI-compatible integration. Instead, it purely relies on a command.

lazygitai-generate-opt.mp4

Adds support for generating commit messages from staged changes using AI, via CLI only.

git:
  commit:
    # Using claude
    aiGenerateCommand: "claude -p 'Generate a conventional commit message for this diff.'"
    # Using opencode
    aiGenerateCommand: "opencode run 'Generate a conventional commit message for this diff.'"
    # Using modelcli
    aiGenerateCommand: 'DIFF=$(git diff --cached) && modelcli "Generate a conventional commit message for this diff. Always provide a bulletpoint body. $DIFF"'

I also made modelcli just for this btw, it has the same exact UX for managing model connections to models.dev as OpenCode... Only simpler, it's not an agent or harness so the start up is faster. (Also in 🦀 rust). This is for people that don't have coding agents installed.

Please check if the PR fulfills these requirements

• Cheatsheets are up-to-date (run go generate ./...)
• Code has been formatted (see here)
• Tests have been added/updated (see here for the integration test guide)
• Text is internationalised (see here)
• If a new UserConfig entry was added, make sure it can be hot-reloaded (see here)
• Docs have been updated if necessary
• You've read through your own file changes for silly mistakes etc

[ruudk]

Why call this ai, this is a command to generate the commit. Has nothing to do with ai.

[Blankeos]

Good call..

Was also thinking of calling it just generateCommand.

Though what do you suggest I hardcode this 'copy' value with?
Generate commit mesage w/ 'generateCommand'?

Or should that copy be configurable? (view here https://github.com/jesseduffield/lazygit/pull/5395/changes#diff-3eb5426752dae525c92f1ecce2f7215d15bfdec91bd459e08f78574876583910)

[ruudk]

Generate commit message

Would be good enough for me or the first version