To switch between branches, type C-u C-x C-q and specify the version number you want to select. This version is then visited unlocked (write-protected), so you can examine it before locking it. Switching branches in this way is allowed only when the file is not locked.
You can omit the minor version number, thus giving only the branch number; this takes you to the head version on the chosen branch. If you only type RET, Emacs goes to the highest version on the trunk.
After you have switched to any branch (including the main branch), you stay on it for subsequent VC commands, until you explicitly select some other branch.
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