git commit

Write the index into a new commit object on the current branch.

🎯 What & why

Snapshot the current index state into a new commit object on the current branch. The commit captures: the tree, your name/email, a timestamp, parent commit(s), and a message. The branch tip is updated to the new commit.

🧠 Mental model

commit is the orchestrator of three plumbing operations: write-tree (turn the index into a tree object), commit-tree (wrap that tree + metadata into a commit object), and update-ref (move the current branch pointer to the new commit). The previous tip becomes the parent. HEAD follows along because it's a symbolic ref.

🛠️ Synopsis

git commit [-a | --interactive | --patch] [-s] [-v] [-u<mode>] [--amend]
           [--dry-run] [(-c | -C | --squash | --fixup) <commit>]
           [-F <file> | -m <msg>] [--allow-empty] [--allow-empty-message]
           [--no-verify] [-e] [--author=<author>] [--date=<date>]
           [--cleanup=<mode>] [--[no-]status] [-i | -o]
           [--pathspec-from-file=<file>] [-S[<keyid>]]
           [--] [<pathspec>...]

🎚️ Switches & options

Flag	What it does
`-m "<msg>"`	Inline commit message. Use `-m "summary" -m "body"` for multi-paragraph.
`-a, --all`	Stage all tracked modifications and deletions before committing. Doesn't pick up new files.
`--amend`	Replace the previous commit (or augment it). Rewrites history — never on shared branches.
`-s, --signoff`	Append `Signed-off-by: Name <email>`. Required by some projects (the kernel, etc.).
`-v, --verbose`	Show the full diff in the editor when composing the message. Encourages reading what you're committing.
`--no-verify`	Skip pre-commit and commit-msg hooks. ⚠️ Almost always wrong.
`-S`	GPG/SSH-sign the commit.
`--allow-empty`	Permit a commit with no changes. Useful for triggering CI.
`--fixup=<commit>`	Create a `fixup!` commit destined to be squashed into `<commit>` on a later interactive rebase.

💡 Use cases

Record what you've staged.
Amend the last commit before pushing (--amend).
Sign off in a project that requires it (-s).
Trigger a re-build by pushing an empty commit (--allow-empty -m 'rebuild').

🧪 Examples

Standard commit with inline message.

$ git add src/main.c
$ git commit -m 'parse: handle empty header'

Commit message with title and body.

$ git commit -m 'parse: handle empty header' \
               -m 'Previously segfaulted on requests with no headers. Empty header maps to an empty string.'

Amend the previous commit (message + index changes).

$ git add forgotten.c
$ git commit --amend --no-edit

Fixup destined to be auto-squashed via git rebase -i --autosquash.

$ git commit --fixup=<sha> --no-edit

🎓 Recommendations

Write commit titles in imperative mood: add foo, not added foo. Title ≤ 72 chars. Body wraps at 72.
Don't --amend after pushing unless you're comfortable force-pushing with --force-with-lease and your team is OK with it.
Use --fixup + git rebase -i --autosquash instead of squashing manually. Robust and reviewable.
Never --no-verify. Fix the hook or remove it; don't bypass it.

🪤 Common pitfalls

git commit -a does not stage new files. People hit this and think their commit is empty.
Empty commit messages are rejected unless you pass --allow-empty-message. There's a reason for that.
Forgetting to set user.email lets you commit, but the commits have whatever default Git guessed. Fix with git config --global user.email "you@host".

🔗 Related modules

📝 Quiz

Hit each option, then Check answers. Score is recorded; Next is always open.