Learning GNU Emacs, 3rd Edition

How VC Helps with Basic Operations

Historically, you had to know three or four different shell commands to do the basic operations of version control (registration, check in, check out, and revert), and you had to do each one outside your editor (or in an editor subshell). This procedure was complicated and annoying, or at best a distraction from the flow of working on your code and changes.

VC's interface is much simpler. The simplicity comes from noticing that whatever state your version-controlled file is in, there is normally just one logical thing to do next. Here are the rules:

• If your file isn't under version control, the next logical thing to do is register it and (where relevant) check out a modifiable copy for you.

• If it's registered, but not checked out by anyone, the next thing you generally want to do is check it out so you can edit it (again, where relevant, such as if you're using CVS in a "keep files read-only unless I say I want to edit them" mode).

• If you have made changes to the file, the next logical thing is to check it back in, which may involve reconciling your changes with those made by someone else.

• Much more rarely, if you're using one of the pre-CVS systems, if someone else has a file checked out, you may want to steal the lock (notifying the lock owner that you've done so).

Indeed, VC mode has just one basic command: C-x v v (for vc-next-action), which you can think of as "do the next logical thing to this file" or, more precisely: "take the currently visited ...