Cheatsheet: Commit hygiene

Voice anchor

Git stores snapshots. Every other command is just navigating those snapshots.

Subject line rules

Rule	Good	Bad
Under 72 chars	Add login form validation	(200-char rambling)
Imperative mood	Fix crash on empty address	Fixed crash on empty address
Capitalized	Add export feature	add export feature
No trailing period	Update README	Update README.
WHAT, not WHY	Refactor address-validator	Made the code better

Commit body structure

Subject line (under 72 chars, imperative, capitalized, no period)
                                                    <- blank line
First paragraph: WHY this change exists. What problem
it solves. What the reviewer needs to know.

Second paragraph (optional): rejected alternatives and
the reasoning. Helps future readers understand why this
approach was chosen.

Closes #1234.

Atomic commit workflow

# Working directory has 3 unrelated changes (files A, B, C)

git status                          # see all 3 changes
git add fileA.js                    # stage only A
git commit -m "Fix crash on empty address"

git add fileB.js                    # stage only B
git commit -m "Refactor address-validator"

git add fileC.js                    # stage only C
git commit -m "Add CSV export to reports"

git status                          # confirm clean tree
git log --oneline                   # see 3 atomic commits

Conventional Commits cheat card

feat(scope): new feature           feat(auth): add OAuth login
fix(scope): bug fix                fix(api): handle null response
docs: documentation                docs: update install guide
refactor(scope): restructure       refactor(checkout): extract validator
test(scope): test changes          test(auth): add password edge cases
chore: maintenance                 chore: bump deps
perf(scope): performance           perf(query): index user_id column
style: formatting                  style: fix indentation

Type indicates change kind. Scope (optional) indicates code area. Description is the imperative-mood subject.

Anti-pattern recognition

Anti-pattern	Example	Fix
Vague verb	fix	Specify what was fixed: Fix crash on empty shipping address
Kitchen sink	Add login and fix nav and update docs	Split into 3 commits
End-of-day megacommit	Day's work	Commit at logical boundaries during the day
Fix-cascade	fix, fix again, actually fix	Test locally before committing; clean up with rebase if not pushed
Body-less complex	Refactor user-service (200-line diff, no body)	Add a body explaining the refactor’s motivation + design

What’s in L4

L4 covers undoing things: git reset (move pointers, modify staging or working dir), git revert (create a new commit that undoes a prior one), git restore (discard working-dir or unstage changes), and git reflog (the safety net that lets you recover almost anything). The skills land directly on top of L3’s hygiene: knowing how to write a clean commit + how to undo a messy one closes the foundational loop.