Anatomy of a good git commit message


Git commits history follows a vicious cycle. If the commit history is unstructured and inconsitent, one doesn't spend much time using or taking care of it. And because it isn't cared for, it remains unstructured and inconsitent.

The importance of good commit messages has been discussed numerous times. And what is a better place to learn it from other than Git itself? Their guidelines to submit patches explains it more comprehensibly.

Follwing are some of the rules which I try to stick by.

Follow a git template.

Follwing is a great template originally written by Tim Pope.

Capitalized, short (50 chars or less) summary

More detailed explanatory text, if necessary.
Wrap it to about 72 characters or so.
The blank line separating the summary from the body is critical (unless you omit
the body entirely); tools like rebase can get confused if you run the
two together.

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.

If you use an issue tracker, put references to them at the bottom,
like this:
Resolves: #123
See also: #456, #789

Write in imperative mode

The use of the imperative, present tense is one that takes a little getting used to. Git is a distributed version control system where there are potentially many places to get changes from. Rather than writing messages that say what you’ve done; consider these messages as the instructions for what applying the commit will do.

If you look at your repository history you will see that the Git generated messages are written in this tense as well - “Merge” not “Merged”, “Rebase” not “Rebased” so writing in the same tense keeps things consistent.

Use conventional commits

The Conventional Commits specification is a lightweight convention on top of commit messages. It provides an easy set of rules for creating an explicit commit history; which makes it easier to write automated tools on top of.

Just prefix the commit message summary with one of following identifiers for a better categorization.

- feat (new feature)
- fix (bug fix)
- docs (changes to documentation)
- style (formatting, missing semi colons, etc; no code change)
- refactor (refactoring production code)
- test (adding missing tests, refactoring tests; no production code change)
- chore (updating grunt tasks etc; no production code change)

Specifying the type of commit in the summary can help finding specific commits more quickly. It also can be used to automatically generate changelogs from your commit logs, e.g. using semantic-release or lerna for monorepos.