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Commit message guidelines

Commit Message Guidelines

Short (72 chars or less) summary

More detailed explanatory text. Wrap it to 72 characters. The blank
line separating the summary from the body is critical (unless you omit
the body entirely).

Write your commit message in the imperative: "Fix bug" and not "Fixed
bug" or "Fixes bug." This convention matches up with commit messages
generated by commands like git merge and git revert.

Further paragraphs come after blank lines.

- Bullet points are okay, too.
- Typically a hyphen or asterisk is used for the bullet, followed by a
  single space. Use a hanging indent.

Example for a commit message

Add CPU arch filter scheduler support

In a mixed environment of…

A properly formed git commit subject line should always be able to complete the following sentence

If applied, this commit will <your subject line here>

Rules for a great git commit message style

  • Separate subject from body with a blank line
  • Do not end the subject line with a period
  • Capitalize the subject line and each paragraph
  • Use the imperative mood in the subject line
  • Wrap lines at 72 characters
  • Use the body to explain what and why you have done something. In most cases, you can leave out details about how a change has been made.

Information in commit messages

  • Describe why a change is being made.
  • How does it address the issue?
  • What effects does the patch have?
  • Do not assume the reviewer understands what the original problem was.
  • Do not assume the code is self-evident/self-documenting.
  • Read the commit message to see if it hints at improved code structure.
  • The first commit line is the most important.
  • Describe any limitations of the current code.
  • Do not include patch set-specific comments.

Details for each point and good commit message examples can be found on https://wiki.openstack.org/wiki/GitCommitMessages#Information_in_commit_messages

References in commit messages

If the commit refers to an issue, add this information to the commit message header or body. e.g. the GitHub web platform automatically converts issue ids (e.g. #123) to links referring to the related issue. For issues tracker like Jira there are plugins which also converts Jira tickets, e.g. Jirafy.

In header:

[#123] Refer to GitHub issue…
CAT-123 Refer to Jira ticket with project identifier CAT…

In body:

…
Fixes #123, #124

Sources

@GeorgeGkas

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commented Jan 6, 2018

With the current version (revision #2) the subject line is ignored by git if it includes an issue id. The second revision introduces a style change in subject format that proposes the use of #<IssueID> at the start of the subject. However, git ignore lines that start with # character thus making the body of the commit the actual subject. I propose to switch back to revision #1 or introduce a different style. We can add the referring issue id to an independent line after the subject. Something like:

Short (72 chars or less) summary

Refer to issue #<IssueId>

More detailed explanatory text. Wrap it to 72 characters. The blank
line separating the summary from the body is critical (unless you omit
the body entirely).

Write your commit message in the imperative: "Fix bug" and not "Fixed
bug" or "Fixes bug." This convention matches up with commit messages
generated by commands like git merge and git revert.

Further paragraphs come after blank lines.

- Bullet points are okay, too.
- Typically a hyphen or asterisk is used for the bullet, followed by a
  single space. Use a hanging indent.

@camh-

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commented Jan 11, 2018

To further support @GeorkeGkas's comment, the summary line is one of the more important parts to get right and with limited space, using it for metadata (the issue ID) is taking away from that limited space.

Most metadata is put at the end of a commit message in a rfc822 header line format.

Fixes: #1234
Signed-off-by: Me me@example.com
Tested-by: You you@example.com
...

If you're just referencing an issue:
Issues: #1234

Just my 2c.

@sorcerykid

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commented Jan 22, 2018

What is the generally accepted practice if a commit contains numerous unrelated changes that cannot be described succinctly in just 50 characters?

For example, if a recent project involves patching a vulnerability in the login handler, removing unused image and sound files, refactoring code and adding better comments, improving performance of the main event loop, fixing bugs in the collision detection algorithm, etc. There is no possible way all of that can fit into a subject line. Yet a generic subject line like "Addressed a lot of lingering issues (see below)" doesn't conform to the conventions described above either.

Any advice would be greatly appreciated. Thanks!

@djanowski

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commented Jan 24, 2018

What to do when including long URLs in the body?

@robertpainsi

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Owner Author

commented Feb 18, 2018

@GeorgeGkas, @camh-, thanks, updated!

@robertpainsi

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Owner Author

commented Feb 18, 2018

@djanowski, you can either

  1. put them on it's own line
Fetching an object is done by using the technique explained at
https://www.url.com/some/very/long/url/that/easily/exceeds/72/characters/per/line
and…

(a line should only exceed 72 characters if the line can't be split. There are also exceptions to this rule, e.g. if you're using code in the commit message)

  1. or reference them
Fetching an object is done by using the technique explained at [1] and…
…
[1] https://www.url.com/some/very/long/url/that/easily/exceeds/72/characters/per/line

Since in many cases the reference is embedded in a paragraph, I prefer the second option. It keeps the line formatting clean and doesn't interrupt your reading.

@robertpainsi

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commented Feb 18, 2018

@sorcerykid, http://whatthecommit.com/ (refresh a few times until you find the commit message that suites your changes 😉)

There isn't really an "accepted practice" here. Maybe you still can split your changes into multiple commits?
Leaving following note here:

Commit Often, Perfect Later, Publish Once

@GeorgeGkas

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commented Mar 11, 2018

I want to propose a possible improvement in References in commit messages section. There are times, not very often but exists, that a commit refers to more than one issue. Most of the times, when this happens, a commit will not refer to more than 2 -maybe 3- issues. To be able to reference multiple issues in the header I propose the following format:

[#123, #879] Refer to GitHub issue…

I would like to read what is your reaction to this update. 😄

@rsp

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commented Apr 17, 2018

@robertpainsi 👍 Excellent guideline, thanks for sharing that. I would only have one comment that I don't generally recommend putting any references to issues or pull requests into the commit message subjects (first line) because I like them to strictly adhere to the "Do something" style with no information that is not meaningful by itself, especially when viewed outside of GitHub like in the command line, or in the case of moving the project to other git hosting, or forking, in which case the issue/PR numbers will be invalid. For that reason I recommend putting those always in the body of the commit message instead. Other than that I think your guideline is really good and I might add some of your commit message rules to my guideline if you don't mind. 😁

@anxiousinc

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commented Jun 26, 2018

Thank you so much for the knowledge.

@pkmandke

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commented May 27, 2019

What is the generally accepted practice if a commit contains numerous unrelated changes that cannot be described succinctly in just 50 characters?

For example, if a recent project involves patching a vulnerability in the login handler, removing unused image and sound files, refactoring code and adding better comments, improving performance of the main event loop, fixing bugs in the collision detection algorithm, etc. There is no possible way all of that can fit into a subject line. Yet a generic subject line like "Addressed a lot of lingering issues (see below)" doesn't conform to the conventions described above either.

Any advice would be greatly appreciated. Thanks!

How about splitting the changes into multiple commits if they are so very unrelated? That would not only make your commit messages specific but also keep similar changes together in one commit.

@shoogle

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commented Jun 6, 2019

How about splitting the changes into multiple commits if they are so very unrelated?

Agreed! This is the only acceptable way to do it. Some projects ask contributors to squash commits together, but this does not usually apply when the commits contain unrelated changes. In fact, unrelated changes should probably be in a separate pull request, let alone a separate commit.

Aim for atomic commits: each commit should do one thing only. Similarly, a pull request should aim to fix one bug or implement one new feature. It should only contain multiple commits if that is required to fix the bug or implement the feature.

If your commit / pull request title contains the word "and" then you probably should have used two commits / pull requests.

@janus007

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commented Jun 13, 2019

Aim for atomic commits: each commit should do one thing only. Similarly, a pull request should aim to fix one bug or implement one new feature. It should only contain multiple commits if that is required to fix the bug or implement the feature.

I seems a bit limited, in the wrong way, that a pull request with one feature, only should consist of one commit. I can easily have 8-10 commits to implement a feature.
The idea with commits are to commit often, so you easily can revert and easily see the progress.
I also often do squashes, but more often I merge master into my branch and I push a couple of 3-4 times a day to my own branch.

@shoogle

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commented Jun 14, 2019

I seems a bit limited [...] that a pull request with one feature, only should consist of one commit.

It's something to aspire to rather than a strict requirement. What counts as "one feature" is ususally determined by what a user wrote in a single issue in the tracker, but we all know that some features are bigger than others. I said multiple commits are allowed, if necessary.

The most important thing is to ensure that that each commit does exactly one thing: no more, no less. Developers look at commits when they try to understand your code changes. If there are too many commits then the history will be too long, but if there are too few then the diffs will be too long and it will be hard to understand what they do from the summary alone.

The idea with commits are to commit often, so you easily can revert and easily see the progress.

Yes indeed, but that is mainly for when you are working on your own branch, and this guide doesn't really apply in that situation. In fact I would recommend you ignore this guide entirely on your own branch, because writing detailed commit messages is a burden that will discourage you from committing early and often. However, once you have got something working, you need to tidy it up a bit before sharing it with other people. That's where this guide comes in, and tools like --fixup and --autosquash help a lot too.

@denismullaraj

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commented Jun 21, 2019

What is the generally accepted practice if a commit contains numerous unrelated changes that cannot be described succinctly in just 50 characters?
For example, if a recent project involves patching a vulnerability in the login handler, removing unused image and sound files, refactoring code and adding better comments, improving performance of the main event loop, fixing bugs in the collision detection algorithm, etc. There is no possible way all of that can fit into a subject line. Yet a generic subject line like "Addressed a lot of lingering issues (see below)" doesn't conform to the conventions described above either.
Any advice would be greatly appreciated. Thanks!

How about splitting the changes into multiple commits if they are so very unrelated? That would not only make your commit messages specific but also keep similar changes together in one commit.

👍

@msihera

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commented Aug 29, 2019

What is the generally accepted practice if a commit contains numerous unrelated changes that cannot be described succinctly in just 50 characters?

@svliantiss

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commented Sep 13, 2019

How do you do this all in the terminal, specifically referencing issues and other commits?

I'd wish there was a way to stage/pause your commit and use the GitHub interface to comment on it before finishing the push or pull request.

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