This was a really interesting read. I'd highly recommend it for anybody who's setting up (or currently maintains) a pre-commit workflow for their developers.
I want to add one other note: in any large organization, some developers will use tools in ways nobody can predict. This includes Git. Don't try to force any particular workflow, including mandatory or automatically-enabled hooks.
Instead, put what you want in an optional pre-push hook and also put it into an early CI/CD step for your pull request checker. You'll get the same end result but your fussiest developers will be happier.
I can second that. If there are multiple commits: https://github.com/tummychow/git-absorb is handy to add formatting changes into the right commit after commits already happened.
To bring up jujutsu, `jj fix` (https://docs.jj-vcs.dev/latest/cli-reference/#jj-fix) is a more refined way of ensuring formatting in commits. It runs a formatting command with the diff in stdin and uses the results printed to stdout. It can simplify merges and rebases history to ensure all your commits remain formatted (so if you enable a new formatting option, it can remove the need for a special format/style fix commit in your mutable set). Hard to go back to pre-commit hooks after using jj fix (also hard to use git after using jj ;) ).
The downside currently (although I've been assured this will be fixed one day) is that it doesn't support running static analysis over each commit you want to fix.
My git rebase workflow often involves running `git rebase -x "cargo clippy -- --deny=warnings"`. This needs a full checkout to work and not just a single file input
I’ve seen similar issues once hooks start doing more than fast checks. The moment they become stateful or depend on external context, they stop being guardrails and start being a source of friction. In practice, keeping them boring and deterministic seems to matter more than catching everything early.
I run this on every commit. Sure, I have probably gone overboard, but it has prevented problems, and I may be too picky about not having a broken HEAD. But if you want to contribute, you don't have to run any pre commit. It'll run on every PR too.
I don't send myself PRs, so this works for me.
Of course I always welcome suggestions and critique on how to improve my workflow.
And least nothing is stateful (well, it caches build artefacts), and aside from "cargo deny" no external deps.
I've worked in several projects where running the tests locally automatically install pre-commit hooks and I've wanted to commit warcrimes because of it.
They are annoying to setup and maintain and contain footguns. I will still use them with prek though because they save dev cycles back-and-forth with CI more than they hurt. I aim to have the hooks complete in under 1 second total. If it saves even a single CI cycle, I think that's a win time wise.
Running on the working tree is mostly okay - just `exit 1` if changes were made and allow the user to stage+commit new changes. It isn't perfect but it doesn't require checking out a new tree.
Your hook can't observe a simple env var, if you are stepping off the happy path of your workflow? E.g. `GIT_HOOK_BYEBYE` = early return in hook script. Article seems a little dramatic. If you write a pre-commit hook that is a pain in your own arse, how does that make them fundamentally broken?
To get a commit history that makes sense. It’s not supposed to document in what order you did the work, but why and how a change was made. when I’m knee deep in some rewrite and realize I should have changed something else first, I can just go do that change, then come back and rebase.
And in the feature branches/merge requests, I don’t merge, only rebase. Rebasing should be the default workflow. Merging adds so many problems for no good reason.
There are use cases for merging, but not as the normal workflow.
That is just not true. Merging is so much less work and the branch history clearly indicates when merging has happened.
With rebasing, there could be a million times the branch was rebased and you would have no idea when and where something got broken by hasty conflict resolution.
When conflicts happen, rebasing is equivalent to merging, just at the commit level instead of at branch level, so in the worst case, developers are met with conflict after conflict, which ends up being a confusing mental burden on less experienced devs and certainly a ”trust the process” kind of workflow for experienced ones as well.
why would you lose commit history? You are just picking up a set of commits and reapplying them. Of course you can use rebase for more things, but rebase does not equal losing commit history.
I commit anything and everything. Build fails? I still commit. If there is a stopping point and I feel like I might want to come back to this point, I commit.
I am violently against any pre commit hook that runs on all branches. What I do on my machine on my personal branch is none of your business.
I create new branches early and often. I take upstream changes as they land on the trunk.
Anyway, this long winded tale was to explain why I rebase. My commits aren't worth anything more than stopping points.
At the end, I create a nice branch name and there is usually only one commit before code review.
Any subsequent commits and the branch are inherently rebased on the squashed commit.
Rebasing is kind of a short hand for cherry-picking, fixing up, rewording, squashing, dropping, etc. because these things don't make sense in isolation.
A bit less enraged: pre-commit hooks should be pure functions. They must not mutate the files being committed. At best, they should generate a report. At worst, they could reject a commit (e.g. if it contains a private key file included by mistake).
In my experience pre-commit hooks are most often used to generate a starting commit message.
To put it more bluntly, pre-commit hooks are pre-commit hooks, exactly what it says on the tin. Not linting hooks or checking hooks or content filters. Depending on what exactly you want to do, they may or may not be the best tool for the job.
To put it even more bluntly, if you are trying to enforce proper formatting, pre-commit hooks are absolutely the wrong tool for the job, as hooks are trivially bypassable, and not shared when cloning a repo, by design.
Yep, all that and they’re also annoying. Version control tools are not supposed to argue - do what you’re told. If I messed up, the branch build will tell me.
The first step of which I usually have as pre-commit run --all-files (using the third-party tool of the same name as git feature) - so running locally automatically on changed files just gives me an early warning. It can be nice to run unit tests locally too, btw.
Is that the difference between forced pre commits vs opt in? I don't want to commit something that doesn't build. If nothing else it makes future bisects annoying.
But if I intend to squash and merge, then who cares about intermediate state.
> I don't want to commit something that doesn't build.
This is a really interesting perspective. Personally I commit code that will fail the build multiple times per day. I only care that something builds at the point it gets merged to master.
so basically, not adhering to atomic commits. That's fine if it's a deliberate choice, but some people like me think commits should stand on their own.
(i'm assuming your are not squashing when merging, else it's pretty much the same workflow)
Honestly, i find that a really weird view. I use (Local) commits for work in progress. I feel like insisting on atomic commits in your local checkout defeats the entire purpose of using a tool like git.
What do you do when you are working on something and are forced to switch to working on something else in the middle of it?
I'm merely the grandparent commenter, not the one you replied to directly, but I can tell you what I do for checkpointing some exploratory work or "I'll continue this next week".
I usually put it on a branch, even if this project otherwise does all its development on the main branch. And I commit it without running precommits, and with a commit message prefix "WIP: ". If it's on a branch you can even push it to not lose work if your local machine breaks/is stolen.
When it's time to get it into the main branch I rebase to squash commits into working ones.
Now, if my final commit history of say 3 commits all actually build at each commit? For personal projects, no. Diminishing returns. But in a collaborative environment: How fun will it be for future you, or your team mates, to run bisect if half the commits don't even build?
I have this workflow because it's so easy to add a feature, breaking 3 tests, to be fixed later. And formatting is bad. And now I add another change, and I just keep digging and one can end up in a "oh no, how did I end up here?" state where different binaries in the tree need to be synced to different commits to even build.
> I feel like insisting on atomic commits in your local checkout defeats the entire purpose of using a tool like git.
WIP commits is hardly the only benefit of git or other DVCS over things like subversion.
Thank you. I don't need to "fix" a commit before it ends up on a remote branch. Sometimes I expect a commit to pass checks and sometimes I don't. Frankly, don't even run pre-push hooks. Just run the checks in CI when I push. You'd better be doing that anyway before I'm allowed to push to a production branch, so stop breaking my git workflows and save me the time of running duplicate checks locally.
Also, if most developers are using one editor, configure that editor to run format and auto-fix lint errors. That probably cleans up the majority of unexpected CI failures.
Pre-commit and pre-push hooks are something developers can voluntarily add (or enable) to shorten the latency until they get feedback: instead of the CI rejecting their PR, they can (optionally!) get a local message about it.
Otherwise, I agree, your project can not rely on any checks running on the dev machine with git.
This was a really interesting read. I'd highly recommend it for anybody who's setting up (or currently maintains) a pre-commit workflow for their developers.
I want to add one other note: in any large organization, some developers will use tools in ways nobody can predict. This includes Git. Don't try to force any particular workflow, including mandatory or automatically-enabled hooks.
Instead, put what you want in an optional pre-push hook and also put it into an early CI/CD step for your pull request checker. You'll get the same end result but your fussiest developers will be happier.
I can second that. If there are multiple commits: https://github.com/tummychow/git-absorb is handy to add formatting changes into the right commit after commits already happened.
> This includes Git. Don't try to force any particular workflow, including mandatory or automatically-enabled hooks.
And with git, you can even make anything that happens on the dev machines mandatory.
Anything you want to be mandatory needs to go into your CI. Pre-commit and pre-push hooks are just there to lower CI churn, not to guarantee anything.
(With the exception of people accidentally pushing secrets. The CI is too late for that, and a pre-push hook is a good idea.)
A good analogy is: git hooks are client-side validation; CI is server-side validation, aka the only validation you can trust.
> with git, you can even make anything that happens on the dev machines mandatory
s/can/can't?
To bring up jujutsu, `jj fix` (https://docs.jj-vcs.dev/latest/cli-reference/#jj-fix) is a more refined way of ensuring formatting in commits. It runs a formatting command with the diff in stdin and uses the results printed to stdout. It can simplify merges and rebases history to ensure all your commits remain formatted (so if you enable a new formatting option, it can remove the need for a special format/style fix commit in your mutable set). Hard to go back to pre-commit hooks after using jj fix (also hard to use git after using jj ;) ).
The downside currently (although I've been assured this will be fixed one day) is that it doesn't support running static analysis over each commit you want to fix.
My git rebase workflow often involves running `git rebase -x "cargo clippy -- --deny=warnings"`. This needs a full checkout to work and not just a single file input
Came here to mention jj fix. It is a fundamentally more elegant way of doing things.
I’ve seen similar issues once hooks start doing more than fast checks. The moment they become stateful or depend on external context, they stop being guardrails and start being a source of friction. In practice, keeping them boring and deterministic seems to matter more than catching everything early.
I feel like I found better git commands for this, that don't have these problems. It's not perfect, sure, but works for me.
The pre commit script (https://github.com/ThomasHabets/rustradio/blob/main/extra/pr...) triggers my executor which sets up the pre commit environment like so: https://github.com/ThomasHabets/rustradio/blob/main/tickbox/...
I run this on every commit. Sure, I have probably gone overboard, but it has prevented problems, and I may be too picky about not having a broken HEAD. But if you want to contribute, you don't have to run any pre commit. It'll run on every PR too.
I don't send myself PRs, so this works for me.
Of course I always welcome suggestions and critique on how to improve my workflow.
And least nothing is stateful (well, it caches build artefacts), and aside from "cargo deny" no external deps.
Only a minor suggestion: git worktrees is a semi-recent addition that may be nicer than your git archive setup
I've worked in several projects where running the tests locally automatically install pre-commit hooks and I've wanted to commit warcrimes because of it.
Don't do that, just dont.
They are annoying to setup and maintain and contain footguns. I will still use them with prek though because they save dev cycles back-and-forth with CI more than they hurt. I aim to have the hooks complete in under 1 second total. If it saves even a single CI cycle, I think that's a win time wise.
Running on the working tree is mostly okay - just `exit 1` if changes were made and allow the user to stage+commit new changes. It isn't perfect but it doesn't require checking out a new tree.
Your hook can't observe a simple env var, if you are stepping off the happy path of your workflow? E.g. `GIT_HOOK_BYEBYE` = early return in hook script. Article seems a little dramatic. If you write a pre-commit hook that is a pain in your own arse, how does that make them fundamentally broken?
why do people rebase so often? shouldn't it be excluded from the usual workflows as you are losing commit history as well?
To get a commit history that makes sense. It’s not supposed to document in what order you did the work, but why and how a change was made. when I’m knee deep in some rewrite and realize I should have changed something else first, I can just go do that change, then come back and rebase.
And in the feature branches/merge requests, I don’t merge, only rebase. Rebasing should be the default workflow. Merging adds so many problems for no good reason.
There are use cases for merging, but not as the normal workflow.
That is just not true. Merging is so much less work and the branch history clearly indicates when merging has happened.
With rebasing, there could be a million times the branch was rebased and you would have no idea when and where something got broken by hasty conflict resolution.
When conflicts happen, rebasing is equivalent to merging, just at the commit level instead of at branch level, so in the worst case, developers are met with conflict after conflict, which ends up being a confusing mental burden on less experienced devs and certainly a ”trust the process” kind of workflow for experienced ones as well.
why would you lose commit history? You are just picking up a set of commits and reapplying them. Of course you can use rebase for more things, but rebase does not equal losing commit history.
I write really poopy commit messages. Think "WIP" type nonsense. I branch off of the trunk, even my branch name is poopy like
feature/{first initial} {last initial} DONOTMERGE {yyyy-MM-dd-hh-mm-ss}
Yes, the branch name literally says do not merge.
I commit anything and everything. Build fails? I still commit. If there is a stopping point and I feel like I might want to come back to this point, I commit.
I am violently against any pre commit hook that runs on all branches. What I do on my machine on my personal branch is none of your business.
I create new branches early and often. I take upstream changes as they land on the trunk.
Anyway, this long winded tale was to explain why I rebase. My commits aren't worth anything more than stopping points.
At the end, I create a nice branch name and there is usually only one commit before code review.
Isn't your tale more about squashing than rebasing?
Any subsequent commits and the branch are inherently rebased on the squashed commit.
Rebasing is kind of a short hand for cherry-picking, fixing up, rewording, squashing, dropping, etc. because these things don't make sense in isolation.
I guess my point is that I disagree that rebasing should be shorthand for all these things that aren't rebasing.
Personally i squash using git rebase -i
Because gerrit.
But even if i wasn't using gerrit, sometimes its the easiest way to fix branches that are broken or restructure your work in a more clear way
I think that only the most absolutely puritan git workflows wouldn’t allow a local rebase.
The sum of the re-written changes still amount to the same after a rebase. When would you need access to the pre-rebase history, and to what end?
really; keep reading about all the problems ppl have “every time I rebase” and I wonder what tomfoolery they’re really up to
A bit less enraged: pre-commit hooks should be pure functions. They must not mutate the files being committed. At best, they should generate a report. At worst, they could reject a commit (e.g. if it contains a private key file included by mistake).
> e.g. if it contains a private key file included by mistake
Thanks - this is the first example of a pre-commit hook that I can see value in.
In my experience pre-commit hooks are most often used to generate a starting commit message.
To put it more bluntly, pre-commit hooks are pre-commit hooks, exactly what it says on the tin. Not linting hooks or checking hooks or content filters. Depending on what exactly you want to do, they may or may not be the best tool for the job.
To put it even more bluntly, if you are trying to enforce proper formatting, pre-commit hooks are absolutely the wrong tool for the job, as hooks are trivially bypassable, and not shared when cloning a repo, by design.
Yep, all that and they’re also annoying. Version control tools are not supposed to argue - do what you’re told. If I messed up, the branch build will tell me.
The first step of which I usually have as pre-commit run --all-files (using the third-party tool of the same name as git feature) - so running locally automatically on changed files just gives me an early warning. It can be nice to run unit tests locally too, btw.
Is that the difference between forced pre commits vs opt in? I don't want to commit something that doesn't build. If nothing else it makes future bisects annoying.
But if I intend to squash and merge, then who cares about intermediate state.
> I don't want to commit something that doesn't build.
This is a really interesting perspective. Personally I commit code that will fail the build multiple times per day. I only care that something builds at the point it gets merged to master.
so basically, not adhering to atomic commits. That's fine if it's a deliberate choice, but some people like me think commits should stand on their own.
(i'm assuming your are not squashing when merging, else it's pretty much the same workflow)
Honestly, i find that a really weird view. I use (Local) commits for work in progress. I feel like insisting on atomic commits in your local checkout defeats the entire purpose of using a tool like git.
What do you do when you are working on something and are forced to switch to working on something else in the middle of it?
I interpreted the parents post as: as long as my combination of commits results in something working before getting merged, it's fine.
Local wip commits didn't come to mind at all
I'm merely the grandparent commenter, not the one you replied to directly, but I can tell you what I do for checkpointing some exploratory work or "I'll continue this next week".
I usually put it on a branch, even if this project otherwise does all its development on the main branch. And I commit it without running precommits, and with a commit message prefix "WIP: ". If it's on a branch you can even push it to not lose work if your local machine breaks/is stolen.
When it's time to get it into the main branch I rebase to squash commits into working ones.
Now, if my final commit history of say 3 commits all actually build at each commit? For personal projects, no. Diminishing returns. But in a collaborative environment: How fun will it be for future you, or your team mates, to run bisect if half the commits don't even build?
I have this workflow because it's so easy to add a feature, breaking 3 tests, to be fixed later. And formatting is bad. And now I add another change, and I just keep digging and one can end up in a "oh no, how did I end up here?" state where different binaries in the tree need to be synced to different commits to even build.
> I feel like insisting on atomic commits in your local checkout defeats the entire purpose of using a tool like git.
WIP commits is hardly the only benefit of git or other DVCS over things like subversion.
Thank you. I don't need to "fix" a commit before it ends up on a remote branch. Sometimes I expect a commit to pass checks and sometimes I don't. Frankly, don't even run pre-push hooks. Just run the checks in CI when I push. You'd better be doing that anyway before I'm allowed to push to a production branch, so stop breaking my git workflows and save me the time of running duplicate checks locally.
Also, if most developers are using one editor, configure that editor to run format and auto-fix lint errors. That probably cleans up the majority of unexpected CI failures.
Pre-commit and pre-push hooks are something developers can voluntarily add (or enable) to shorten the latency until they get feedback: instead of the CI rejecting their PR, they can (optionally!) get a local message about it.
Otherwise, I agree, your project can not rely on any checks running on the dev machine with git.
I don't want roundtrips to my CI which easily takes a minute and pushes me to look at yet another window. Pre-commit hooks save me so much time.