underlap

A micro-commit is a commit of a small/incremental code change, which ideally also passes the tests.

Micro-commits combine nicely with TDD as follows: 1. Write a failing test 2. Make all the tests pass 3. Commit 4. Refactor to make the code clean 5. Commit

Why commit so often?

Mark Seeman's recent stackoverflow blog “Use Git tactically” uses one of my favourite analogies to coding: rock climbing. The basic idea of micro-commits is to work with small, safe changes and commit after each one, much as rock climbers regularly secure their ropes to the rock face.

If something goes wrong, there's a smaller distance to fall. In coding, something going wrong, such as a regression creeping into the code, can be recovered from by returning to an earlier commit without losing much work in the process.

Other benefits

Using micro-commits reduces the stress of coding. Not only do you know you're not going to lose much work if you mess things up, but by focussing on one small step at a time, you don't have to keep a lot of information in your head.

Micro-commits also help you stay focussed on making just one change at a time. To avoid falling into the “While You’re At It” trap, described in Tim Ottinger's blog “What's this about Micro-commits?”, keep a TODO list, either in an issue or, for short-lived items, on a piece of paper.

Squash or merge?

After completing a fix, feature, or other pieces of work, it's important to decide what to do with all the micro-commits.

One approach is to squash them into one or more substantial commits. A downside of squashing is that there is then no record of the sequence of micro-commits, which could come in handy (e.g. for bisecting out a bad change) if some problem has crept in which didn't show up while running the unit tests. An advantage of squashing is that people reading the commit history can then see the wood for the trees.

Another approach is to merge the changes with a commit message that summarises the changes. It's hard to see the wood for the trees in this approach when reading a linear series of commit messages (such as produced by git log), but tools which show the commit structure make it easy to pick out the merge commits.

Commit messages

Commit messages for micro-commits are likely to be brief, but don't forget to reference any associated issue(s). You may want to treat the commit messages like a discussion thread and drop in the occasional comment on the overall design when it occurs to you rather than forget to include it when you finally squash or merge.