Wrong branch and detached HEAD

The most common slip: you meant to start a branch, forgot, and committed straight onto main. If you haven't pushed, it's a quick fix. A branch is just a label, so first create one where you are now (your commits come with it), then move main back to where the remote has it. Stash any uncommitted edits first, because reset --hard discards them.

git switch -c feature/discount   # a new label at your commit, and you're on it
git switch main
git reset --hard origin/main     # main goes back to what GitHub has

If the branch you meant already exists, copy the commit over with git cherry-pick. It replays one commit onto the branch you're on, as a new commit with a new ID. Then take it off main the same way.

git switch feature/discount
git cherry-pick e4f5a6b          # copy that commit here
git switch main
git reset --hard origin/main

The other way to end up in the wrong place is detached HEAD. Checking out an old commit to look at it (git switch --detach a1b2c3d, or git checkout a1b2c3d) puts you on no branch at all. Looking around is harmless. Committing there is the trap: those commits belong to no branch, and when you switch away, git warns that you're leaving them behind. Give them a branch before you leave, with git switch -c <name>.

$ git status
On branch main
Your branch is ahead of 'origin/main' by 1 commit.
  (use "git push" to publish your local commits)

$ git switch main
Warning: you are leaving 1 commit behind, not connected to
any of your branches:

  38ddf90 Try new layout

If you want to keep it by creating a new branch, this may be a good time
to do so with:

 git branch <new-branch-name> 38ddf90

Switched to branch 'main'

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