git switch: move between universes

When you run git switch feature, your files change. Files created on feature appear; files deleted there vanish; edits made there are suddenly in place. Nothing is lost — every version of every file is safe in the album — but your working folder is rewritten to be feature's universe.

It feels like teleportation. It is really just git materialising the photograph that feature's label points at. One folder, many universes, and the switch command decides which one you are standing in.

One exception travels with you: untracked files — files no photograph has ever included — come along across switches. Git treats them as none of the universes' business, so they just sit there while the tracked world shifts around them.

Two commands are typed together so often that git combined them: git switch -c feature creates the branch and steps onto it in one go. The -c means create. In real work you will use this constantly — new idea, new branch, one command, start working.

You will also constantly see an older spelling: git checkout feature does the same move, and git checkout -b feature is the old create-and-switch. Checkout is the grand old command that does many jobs; switch was added to do exactly this one job with an impossible-to-confuse name. Both work everywhere. This simulator understands both.

If you have edited a tracked file and not committed it, switching branches could overwrite that edit — so git refuses: error: Your local changes would be overwritten by checkout, plus the name of the file, plus Aborting. Nothing happened; your work is intact; git just declined to gamble with it.

The fix is always the same and always boring: commit your work first, then switch. A commit takes ten seconds and makes the switch safe. Git blocking you here is not an error — it is git being the friend who takes your drink away before you text your ex.