Squash

Squashing in Git, refers to the process of combining multiple commits into a single commit. This is often done to create a cleaner and more concise commit history, especially before merging a feature branch into the main branch.

Why bother

A branch built one commit at a time accumulates the small corrections that belong to no single idea: a typo fix, a forgotten file, a rebase that got the message wrong. Squashed into the commit they belong to, the history reads as one change per idea — which is what a reviewer, a git log, and git bisect all want.

Interactively

git rebase -i HEAD~5

Git opens the last five commits in an editor:

pick a1b2c3d add search endpoint
pick d4e5f6a fix typo in route
pick g7h8i9j add tests
pick j1k2l3m wip
pick m4n5o6p fix typo again

Change pick to squash (or s) on the commits that belong to another, save, and Git folds them in, asking you to combine the messages.

pick   a1b2c3d add search endpoint
squash d4e5f6a fix typo in route
squash m4n5o6p fix typo again

fixup (or f) is the same without the message prompt — it discards the squashed message and keeps the target's. drop removes a commit entirely, and reordering the lines reorders the commits.

Amend the last one

git commit --amend
git commit --fixup <hash>
git rebase -i --autosquash HEAD~5

--fixup stages a correction as its own commit, and --autosquash folds those in automatically when you start the rebase. If you find yourself making a lot of small corrections, that pair is faster than fixing them by hand.

Once it is shared

Squashing rewrites hashes. Do it on your own unpushed branch, or on a pull request nobody has pulled yet. Doing it to a branch other people have already fetched makes their history and yours disagree — see Rebase.

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