top | item 44345334

Git Notes: Git's coolest, most unloved­ feature (2022)

579 points| Delgan | 8 months ago |tylercipriani.com

145 comments

order

oftenwrong|8 months ago

Another little-known feature is git trailers:

https://alchemists.io/articles/git_trailers

These are key-value structures data that can be included on a commit when it is created. These are used by some systems for attaching metadata. For example, Gerrit uses this for attaching its Change-Id.

oftenwrong|8 months ago

One more similar feature from a different system: PostgreSQL COMMENT

https://www.postgresql.org/docs/17/sql-comment.html

This allows you to attach text to various database objects in PostgreSQL.

I wish PostgreSQL had a feature that was more like structured key-value database object metadata that could be edited.

_flux|8 months ago

I used git notes for marking which of my commits in my branch I had run the unit tests for (and thus my script would skip those). This was useful when working with open source upstream where you want the massage the branch to perfection with git rebase -i.

It seems git trailers would now be the better place to put that information.

Regarding change ids: I wish git itself had those, as then also the tooling would understand them. Identifying commits by their commit messages is fragile, in particular when you may update those for an MR. While commit id truly identifies the commit in a unique way, it is not a useful identifier when the same changes could be moved on top of some other commit.

edit: Oh it looks like they are actually part of the commit, whereas notes aren't, so it wouldn't be a good replacement for my use.

imiric|8 months ago

Interesting, I wasn't familiar with this feature.

I'm a big fan of conventional commits, and trailers seem like a better way of adding such metadata.

Is adding them manually to the commit message functionally equivalent to using the `--trailer` flag?

cmrdporcupine|8 months ago

Side note: I really miss Gerritt from my time working at GOOG, but man is its deployment story kinda crap in the 2020s. I tried to run an instance locally and was hoping to integrate it with my github hosted repo ended up just frustrated.

Is there anything equivalent -- that handles tracking changes over commits etc better than GH -- that is more actively developed and friendly for integration with GH? I hate GH's code review tools with the heat of 10,000 suns.

adregan|8 months ago

While I mostly try to go with the flow, I do get frustrated that there are more natural places to integrate with a issue tracking system like trailers, but they are so far off issue trackers’ happy path that it’s not worth it.

I think the problem is exacerbated by the fact that issue trackers follow fashion; and it’s more common that you are using the flavor of the week; and that flavor isn’t close to feature complete; and new features get added at a glacial pace.

I suppose this is a long winded way of stating how annoyed I am with branch names derived from linear ticket’s titles for tracking purposes, and I wish I could use some other form of metadata to associate commits with an issue, so that I could have more meaningful PR titles (enforced that I must use the linear branch name as the title).

Though I’ll admit that it’s an issue of a size that’s more appropriate to gripe about on the internet than try to change.

Ayesh|8 months ago

TIL the `--trailer` CLI option. I used to edit the commit message in a text editor and manually add the trailers (which works for GitHub `Co-Authored-By`).

being able to use them with `git log` format is pretty cool.

EPWN3D|8 months ago

Yeah I love trailers. I remember trying to use notes for certain things, and they were just kind of a pain (though I cannot remember exactly what roadblocks I hit). Trailers met my needs nicely.

stephenlf|8 months ago

This is fantastic. This could really beef up CI with ticket numbers and stuff.

jes5199|8 months ago

oh I have use of that, never heard of it

xg15|8 months ago

Sounds really cool, but how do notes play together with the "history rewriting" features (amend, rebase, etc) where you effectively replace a commit with a modified copy? It sounds as if the notes are attached to a specific commit (or tree or blob) ID. Are git rebase etc smart enough to also copy over the notes to the new commit, or will they just vanish?

What happens on interactive rebases, e.g. if I squash multiple commits into a single one?

I see the same problem with attaching notes to blobs and trees: It's not doing what you might think it does: It feels like it would attach metadata to a file or directory in the repo, but it really attaches the metadata to some specific content:

E.g. if you have a blob that encodes the string "Hello world!" and attach the note to it, would git associate that note with all files that have that content?

Also, if you change one file to "Hello, world!", would it lose the notes?

rlpb|8 months ago

> Are git rebase etc smart enough to also copy over the notes to the new commit...

This is configurable. By default, amend and rebase operations will copy them forward. See git-config(1) under `notes.rewrite`.

akoboldfrying|8 months ago

I've been using git for probably 10 years and I didn't know git notes existed. Cool!

> Here is a plea for all forges: make code review metadata available offline, inside git.

I think this will fall on deaf ears as far as commercial forges like GitHub go, since as you yourself observe:

> But much of the value of git repos ends up locked into forges, like GitHub.

For-profit enterprises are not generally excited about commoditising their own value-add. This is not a jab at GitHub -- I think GitHub do everything right (offer a great service, a very generous free tier, and make it possible to extract all your data via API if you want to shift providers). It's just the nature of any commercial operation.

esafak|8 months ago

You have to start a new service that offers that feature as one of its differentiators, then the competitors might add it (back) to catch up.

kccqzy|8 months ago

Git notes are only cool if you frequently add text to a commit after the commit has happened and visible to others.

The Acked-By and mailing list discussion link examples don't seem to be good examples. Both of these are likely already known when the commit is made. And git commit message basically can have an unlimited length, so you could very well copy all the discussions about the commit that happened on a forge into the commit message itself.

One use case I think might be a better example is to add a git note to a commit that has later been reverted.

hinkley|8 months ago

The common failure mode is commit messages proudly proclaiming they fixed a bug that they did not. And linking knock-on bugs created by their fixes to one bug.

Maybe I’m weird that way. I’ve had too many coworkers who don’t really even look at annotations to remind themselves why this code was written in the first place. They will just yolo and hope nobody ties the problems back to them. But once you’ve dealt with an irate customer who waited impatiently for a bug to be fixed, and only to have the bug be reintroduced a short time later, you may become more circumspect about bug fixes.

There’s often a refactor needed to fix multiple bugs at once. There’s often refactor can open up new feature opportunities, or performance improvements.

Zambyte|8 months ago

> The Acked-By and mailing list discussion link examples don't seem to be good examples. Both of these are likely already known when the commit is made.

Discussion regarding a commit (is: review) and acknowledgment of a commit cannot happen before the commit has been made.

> One use case I think might be a better example is to add a git note to a commit that has later been reverted.

Commit messages are better for this use case. When you got blame a file, it shows the latest changes for that file. If a commit reverts changes from another commit, the newer commit that reverts the older commit will show up in the blame.

0x696C6961|8 months ago

Discussion can keep happening after the commit is created.

noelwelsh|8 months ago

This is a UI problem, not a lack-of-knowledge problem. If Github's UI surfaced notes they would instantly get much more usage.

stephenlf|8 months ago

Yeah I wish GitHub supported these

lucasoshiro|8 months ago

There are many "Git's coolest, most unloved feature", e.g.: bisect, pickaxe, reflog, range-diff, archive, annotated tags, etc. Sadly they are often forgotten as many people thing of Git only as a glorified Google Drive...

knallfrosch|8 months ago

Git notes is redundant since you need a higher-level project management tool to track features anyway. Roadmaps, feature hierarchy and non-technical details. Think of any big tracker or Jira.

I think that's fine. Unix philosophy is to focus on one thing and do that well.

pydry|8 months ago

In many cases this is because those features arent actually that useful and they are frivolities surrounding a workhorse.

steve_adams_86|8 months ago

Ha, I expected to know the features you were going to list, but got surprise attacked by pickaxe. What the hell? I guess I shouldn’t be so confident

cesarb|8 months ago

Git notes were used at the LibreOffice project to track, for each commit to the Apache OpenOffice repository (which they mirrored as a branch on LibreOffice's git repository), whether that commit was not relevant (for instance, changes to the build system which LibreOffice had long replaced with a better one), duplicated an already existing change on LibreOffice (often from many years earlier), or, the least common case, that it was accepted into LibreOffice (and which commit did the cherry-pick). You can still see it for itself at https://cgit.freedesktop.org/libreoffice/core/log/?h=aoo/tru... (that git front-end still displays notes).

(They stopped tracking these changes a few years ago, probably because the pace of changes to Apache OpenOffice slowed down to a trickle, and there's no longer much to be gained by cherry-picking these few changes.)

ozim|8 months ago

It is not coolest most unloved feature. It is a gimmick feature that could have been cool in some really specific cases like team of only developers running the whole company.

Whatever is needed goes into commit message and referencing tickets in separate system is a feature not a bug - because JIRA or any other system is used to communicate with non developers. Like business analysts don't get access to code or repositories at all for example or support people don't get access to the repositories and code.

Yeah I can see how one could write front end to get the notes visible/editable by non developers but it still does not make any sense because BA/Support others don't care about specific commits and a single feature might fit into a commit but most likely does not. Even more fun is when you have multi repo and your feature touches couple services then git notes are quite useless because then you really need reference to outside system.

stopthe|8 months ago

> business analysts don't get access to code or repositories at all for example or support people don't get access to the repositories and code.

Yes, but isn't it insane? What is the benefit from treating your own product as a black box? Yet that's mainstream. Sometimes I have the analyst (not on my team, but from a team we share a monorepo with) asking me questions that can be answered literally with a line of code. And she's a technical kind, knows SQL and such. And we write very idiomatic, high level code. But still, culture cannot change itself until it dies due to inherent inefficiency.

chrishill89|8 months ago

There’s plenty of data which is extra-commit (doesn’t belong in the commit messages but is relevant). Like if the tests passed[1], manual testing notes, iteration on code review, notes for code spelunking when you find a problematic 6+ month old commit.

[^1] https://news.ycombinator.com/item?id=44348438

EricRiese|8 months ago

A 9 year old feature request for notes support in GitLab was closed recently

https://gitlab.com/gitlab-org/gitlab/-/issues/15029

You have to log in to read it unfortunately, but any gitlab.com account should work.

opello|8 months ago

To save people from wondering, it was closed for abandonment and not completion:

> This feature request is being closed as our current focus isn't in this area.

legends2k|8 months ago

I discovered notes from the man pages around 2020 but didn't use them as it was primarily a local repo feature. By default they don't get pushed or fetched. If course, one can configure it such that it's pushed and fetched, but that's a team decision and mine didn't vote for it.

WorldMaker|8 months ago

I feel like notes needs a more similar default to tags' updated defaults today: fetched/pulled by default but not pushed by default. It is useful to keep personal tags and personal notes and some people have workflows involving those, but once tags/notes are in the upstream repository, it should maybe be assumed that everyone should know about them.

olejorgenb|8 months ago

What happens of you rebase a branch containing commits with notes attached?

paffdragon|8 months ago

I wrote a little tool for versioning based on conventional commits that uses git note for a version override. In case you want to force a specific version instead of the one autodetected, you can add a git note with the version you want.

This was useful when migrating a piece of functionality into its own repo and you want to preserve history. Adding these forced version tags into commits would be quite messy in the new repo where you switch to a new versioning scheme.

Shank|8 months ago

Why did GitHub remove support for them, and how do we get this decision reversed?

fmbb|8 months ago

I think the answer is in the link.

Making git notes more usable would make it easier to migrate from GitHub. It would make you less locked in.

chrishill89|8 months ago

I use Git Notes all the time. It doesn’t look like the article mentions that you can attach the notes to emails you send out with git-format-patch(1) and git-send-email(1). I use them for emails to attach comments on patches that shouldn’t go into the commit message:

    I did <insert research notes> and found no other places in the code base where this needs to be fixed.
And as the cover letter for a single patch (if needed/not cowered by the commit message).

And also like a commit message on the iterations on the patches. So for a patch series that go over three versions the note may say what updates where done in versions 2 and 3.

And other than that I use notes for:

- Private notes on how I’ve manually tested the commit

- Link to CI

- A localized changelog for customers (who are not technical)

pettereriksson|8 months ago

I think it would be interesting to add the prompt (or a summary of the prompt) as a note for each commit. This would allow the LLM to later reason about each line of code by going back and checking the notes to mine for requirements, and take those into account when changing the code again.

lozenge|8 months ago

Or just put it in the commit message, after all, it is the human's description of what the commit is supposed to do

marcodiego|8 months ago

I bet it already exists, but what about an issue tracker in plain text maintained by git itself?

lelanthran|8 months ago

> I bet it already exists, but what about an issue tracker in plain text maintained by git itself?

I have an issue tracker file that can be added to a project. While it's technically plain text, the interface for the file ensures that a format is used, and the format ensures that changes reflect only a single ticket.

Just as long as no one edits the file using a different program, it will work just fine.

Don't think anyone uses it, though.

https://github.com/lelanthran/rotsit

righthand|8 months ago

Also checkout fossil-scm.org

minikomi|8 months ago

This seems an interesting thing to explore for adding extra context to coding agents.

rpicard|8 months ago

This would be a cool place for LLMs to store a summary of the prompts used to generate the code in order to make it easier for other LLMs and humans to pick up where they left off.

fudged71|8 months ago

I've been thinking about this exact same problem. It would be great to store a log of how much time/tokens were spent reasoning, what was the reasoning path, why were certain decisions made, etc.

I don't know if rationale is something better suited for the git commit log, or tagged by code function to an external "rationale" system of record.

lrvick|8 months ago

A few years ago I wrote a simple git "extension" that allows you to attach signatures to existing git commits, and allow for verification that a minimum number of signatures from relevant teams exist. This is possible because Git Notes allow you to attach and distribute arbitrary metadata with any commit ref.

https://git.distrust.co/public/git-sig

lars512|8 months ago

I had a good use case at Our World In Data for the public data pipeline, where one repo had the pipeline and one git-lfs repo had the build output of the pipeline. A git note added to a commit to the code pipeline recorded the hash identifying the built data.

Overall it felt elegant, and needed no maintenance after setting it up, but honestly it was never used. I think the need to look back in time was rarer than expected, and git notes being hidden by default didn’t help for awareness.

johnisgood|8 months ago

Is there a list of not-really-known features of git (such as git notes, git trailers, etc.)? I have been using git for decades but I have not yet came across of these two.

remram|8 months ago

In practice I get a lot of value out of referencing commit hashes. If I fix a problem I introduced in a previous commit (for example, commit bumped version, and I forgot to bump it somewhere), my fix will say "amends ab12cd34".

That way when I need to cherry-pick that commit, or do something similar (bump again), I can search for the hash of the commit I'm looking at to find what might be missing.

UI is worse than git-notes but no need for additional setup to sync them.

codesnik|8 months ago

you kinda doing by hand what git commit --fixup could do for you, and what git rebase -i could pick up automatically.

grahar64|8 months ago

I tried using git notes for distributed secure reviews but hit some road block with merges. It is a good idea that has limitations that limit its adoption

remram|8 months ago

What are the limitations?

nop17|8 months ago

If note just for the last commit, would it easier just amend the last commit message to include any note? Don't need remember another command option.

mtillman|8 months ago

OP suggested that they are unused because of the awkward interface but I find that if you were taking notes in text about a release, you can easily pipe those notes to Git Notes on commit. This seems easy to me. Am I missing something?

827a|8 months ago

Why would I choose to stash information like this in the git notes, versus just appending it to the commit message itself?

zygentoma|8 months ago

Because you would not want to write the whole git history starting from the commit you want to stash this info one everytime you want to stash additional info …

Appending information to the commit itself creates a new commit and all the commits that are based on the commit will also have to change consequently.

r-bryan|8 months ago

Methinks Zawinski's Law of Software Envelopment finds some empirical support here.

zackmorris|8 months ago

This is great! And how did I not know about this? My favorite days are when I learn something new. Even better are when I learn that I was wrong and change my mind to improve my thinking. So meta!

Git notes would be ideal for annotating commits that contain commit hashes used as breadcrumbs to inform the developer (usually me months later) about context around previous work. These hashes might have changed due to a rebase or from using disk space optimization tools that rewrite history like these:

https://rtyley.github.io/bfg-repo-cleaner/

https://github.com/rtyley/bfg-repo-cleaner

https://github.com/newren/git-filter-repo

https://github.com/tiavision/GitRewrite

See also:

https://stackoverflow.com/questions/5613345/how-to-shrink-th...

https://stackoverflow.com/questions/1398919/make-git-consume...

https://stackoverflow.com/questions/2116778/reduce-git-repos...

https://stackoverflow.com/questions/3119850/is-there-a-way-t...

https://stackoverflow.com/questions/38789265/git-delete-some...

https://stackoverflow.com/questions/16057391/git-free-disk-s...

https://stackoverflow.com/questions/31423525/how-to-reduce-d...

https://stackoverflow.com/questions/16854425/compact-reposit...

https://stackoverflow.com/questions/13999191/trimming-huge-g...

https://stackoverflow.com/questions/4515580/how-do-i-remove-...

These methods are all uniquely terrible in various ways. Most likely user error on my part. I need this technique:

1. Choose a range of commit hashes (or hashes before a commit) and remove them. This can be useful when splitting repos, for example on projects that started as backend+frontend where the frontend is being forked off in a new repo and the older backend portion needs to be removed from it for security/privacy.

2. Rebase all branches (including those that crossed the deleted portion) to preserve their structure but start/end as recently as possible. Optionally discard branches that were created and merged entirely within the deleted ported, unless they're the trunk of other branches that merge after the deleted portion.

3. Search for old commit hashes in commit messages and update them to the new hashes while rebasing.

4. Bonus points for updating stashes (or other git features) having any commit hashes in their names. Also for importing/exporting a list of important commit hashes for use in project management, such as updating hashes in comments on kanban boards like Jira.

5. More bonus points for searching for large files (such as app.js or other build artifacts) so that they can be stripped from commits in branches, preferably not on a main trunk like master.

If you followed this far, I could also use a technique that rebases merged branches so that they form a series of D shapes instead of overlapping B shapes (this is useful during git bisect). Ideally this would happen automatically or be enforced via rules on sites like GitHub and GitLab. I always rebase my branches before merging, but others can't be bothered.

https://www.atlassian.com/git/tutorials/merging-vs-rebasing

Where I'm going with this: I git reset and git cherry-pick constantly in my own branches before merging, so that each branch has a clean work history like the trunk. I think of this as quantum committing, because I keep exploring the problem space until I find a solution that collapses (merges) into the history.

The problem is that git GUIs are inadequate for this work. I need to be able to cut/copy/paste commits, drag and drop them for reordering, etc. It should also derive the commit diff needed to make a commit match a branch (or folder) rather than throwing a conflict in my face, so that it operates more like Apple's Time Machine. If I had this app, I could simply select all commits that I wanted to delete, it would ask me "this rewrites history, are you sure?", and then delete them and do the right thing for affected branches. It would also have infinite undo powered by git reflog.

The idea being that commit hashes should not take priority - it's all about the information. We should never be trapped by the state of the repo, because that creates anxiety.

So we're missing a tool to orchestrate git the way that Kubernetes orchestrates Docker.

hungryhobbit|8 months ago

Coolest? It's just extra comments...

b0a04gl|8 months ago

i use git notes pretty heavily in my current role. started as an experiment to keep track of internal code reviews without flooding the commit message or making PRs for everything. i tag every commit with context what tickets it maps to, infra constraints, links to incident threads if it's a fix. all lives in the repo. this avoids the need to grep slack or jira just to know why a line changed. nce you start using it at scale, you realise how little you need the platform UI at all. we keep talking about reproducibility in builds, but never in intent. maybe this is where that starts

smallpipe|8 months ago

Shouldn’t that be the commit message ? Or is the goal to also link forward in time, such as “we realised this commit introduced bug #123” ?