Git: Support run `prepare-commit-msg` hooks

[thomasheartman]

Summary

Zed doesn't run prepare-commit-msg hooks when you start a commit message.

Steps to trigger the problem:

1. Have an active git repository
2. Add a prepare-commit-msg hook
3. Invoke git commit via the git command line, using the $EDITOR variable. Notice that the hook modifies the content of your buffer
4. Start a commit message via Zed: the message is empty

Actual Behavior:
The prepare-commit-message hook does not affect the commit message editor

Expected Behavior:
The prepare-commit-message hook should be run and allowed to edit the commit buffer.

Context

This isn't a crucial thing to my workflow, but I'm opening the issue for it because @mikayla-maki asked me to when I reported it in the discord.

I've been using the hook for the last couple of years to automatically populate my commit message with the commit type (using conventional commits) and optionally the task number in whatever work tracking system we use.

Typically, I'll name a branch something like chore/do-the-thing or fix(1-26)/doesn't-work. The commit hook then looks at the current branch name, extracts everything before the first slash, and inserts it into the commit message.

As a bonus: I've made it so that if I'm on the main branch of a repo, it'll insert a comment in all caps reminding me that I haven't created a branch yet. I can dismiss this, of course, but often times I've just forgotten to actually create a branch, so it's quite helpful.

If it's helpful, here's the script I use

My current prepare-commit-msg script

#!/usr/bin/env bash
COMMIT_MSG_FILE=$1

CURRENT_BRANCH=$(git rev-parse --abbrev-ref HEAD)

IFS='/'
if read -r _ DEFAULT_BRANCH <<< "$(git rev-parse --verify -q --abbrev-ref origin/HEAD)" && [ "$DEFAULT_BRANCH" = "$CURRENT_BRANCH" ]; then
    MESSAGE="; YOU'RE ON THE DEFAULT BRANCH.\n"

else
    extract_branch_prefix() {
        if [[ $1 == *"/"* ]]; then
            cut -d '/' -f 1 <<< "$1"
        else
            cut -d '-' -f 1-2 <<< "$1"
        fi
    }

    TASK_TYPE="$(extract_branch_prefix "$CURRENT_BRANCH")"
    MESSAGE="${TASK_TYPE}:"
fi

if [ -z "$(head -n 1 "$1")" ]; then
    sed -i "1s/^/${MESSAGE}/" "${COMMIT_MSG_FILE}";
fi

---

Finally, I'm assuming that the hook is never run, because Zed doesn't invoke git commit and setting itself as the $EDITOR. I'm assuming it just passes the commit message as a string to git commit, thus bypassing prepare-commit-msg (and potentially other hooks related to the msg).

As for the actual implementation: because Zed allows you to toggle the commit window whenever you want, it might be hard to know when to run the hook. I'd think it makes sense to run the first time you open an empty message and have staged hunks? It should probably never clobber anything you have in there already.

Zed Version and System Specs

Zed: v0.179.1 (Zed Preview)
OS: macOS 15.3.1
Memory: 16 GiB
Architecture: aarch64

[notpeter]

This seems like a reasonable request and something which we should perhaps try to support.

Given that it is currently possible to type a commit message in the git panel at any time (not just when running git commit) I'm not sure the best design to support such functionality.

Perhaps a manual button?
Alternatively, it might also be possible to create settings opt-in flow which disables the commit message box in the git panel and clicking the commit button follows the traditional git commit flow of popping a new buffer (after firing pre-commit-msg hooks of course).

Curious if you know how this is handled in other editors (vscode, jetbrains, etc)?

Thanks for reporting.

[thomasheartman]

Sorry, I must've missed the response you posted a month ago.

I agree that how to design it because you can always type the message is hard. A button feels like it'd be too much work (suddenly it's not run automatically anymore). But at the same time, how do you know when to run it?

I think my preference would be to run it (or at least insert it) whenever you open the commit text area (not the git panel, just the text input) and there is no text in there already. I think that'd be the closest to what I'm used to.

And speaking of: I don't know how vscode or jetbrains handles this, but I know roughly how Emacs/magit handles it. With magit, when you run the commit action, it'll run all the regular pre-commit hooks before opening a text buffer for the commit message. In essence, this is the same as running git commit in a shell, except that the commit editor is a new emacs buffer instead of whatever you've got your editor set to. Any output (such as wheat I've done in my hooks) will be inserted into the buffer the same as it would into a normal commit editor buffer.

If you abort the commit and then run the commit action again, it'll tell you there's already an active file and ask you if you want to resume editing that one, or start a new one.

I think we could do the same in Zed with the approach outlined above. When you call git::Commit (or otherwise open the floating panel and maybe when you focus the input in the git panel), run the hooks and insert the output into the text box.

If there's content there already, do nothing. If you remove the content and take focus away from the input, maybe we should run the hooks again the next time you focus? 🤷🏼

But you might have much better ideas for this, so I don't want to be overly prescriptive.

[notpeter]

I'm realizing I've never operated in an environment with prepare-commit-msg hooks, only pre-commit and pre-push, so I'm having to bend my brain a bit here. In many ways prepare-commit-msg in some environments seems similar to the "Generate Commit Message" button may operate, but it does so with scripts instead of a remote LLM.

In the meantime, as a workaround, you could create a custom task for git commit, e.g.:

[
  {
    "label": "GitCommit",
    "command": "git commit",
    "env": { "EDITOR": "zed" }
  }
]

And then create a custom keybinding for it.

Inherently, the prepare-commit-msg is something which is not designed to be run async -- it assumes you will be waiting for it to finish before you are allowed to edit a commit message that it pre-populated. It assumes there is always a step in the workflow for it to be triggered:

git commit -> prepare-commit-msg > COMMIT_MESSAGE -> $EDITOR COMMIT_MESSAGE

But the Zed GUI Git commit workflow is much closer to git commit -m "message" and there's no place for prepare-commit-msg to wedge itself. Conceivably, if a prepare-commit-msg hook is detected, the Zed commit message textbox could be disabled and replaced with a "Prepare Commit Message" -- clicking that button would initially populate the commit message and re-enable the textbox. It's still pretty niche though.

[github-actions]

Hi there! 👋
We're working to clean up our issue tracker by closing older bugs that might not be relevant anymore. If you are able to reproduce this issue in the latest version of Zed, please let us know by commenting on this issue, and it will be kept open. If you can't reproduce it, feel free to close the issue yourself. Otherwise, it will close automatically in 14 days.
Thanks for your help!