28.1.13.3 Options specific for CVS

You can specify additional command line options to pass to all CVS operations in the variable vc-cvs-global-switches. These switches are inserted immediately after the cvs command, before the name of the operation to invoke.

When using a CVS repository on a remote machine, VC can try keeping network interactions to a minimum. This is controlled by the variable vc-cvs-stay-local. There is another variable, vc-stay-local, which enables the feature also for other back ends that support it, including CVS. In the following, we will talk only about vc-cvs-stay-local, but everything applies to vc-stay-local as well.

If vc-cvs-stay-local is only-file (the default), VC determines the version control status of each file using only the entry in the local CVS subdirectory and the information returned by previous CVS commands. As a consequence, if you have modified a file and somebody else has checked in other changes, you will not be notified of the conflict until you try to commit.

If you change vc-cvs-stay-local to nil, VC queries the remote repository before it decides what to do in vc-next-action (C-x v v), just as it does for local repositories.

You can also set vc-cvs-stay-local to a regular expression that is matched against the repository host name; VC then stays local only for repositories from hosts that match the pattern.

When using a remote repository, Emacs normally makes automatic version backups of the original versions of each edited file. These local backups are made whenever you save the first changes to a file, and they are removed after you commit your changes to the repository. (Note that these are not the same as ordinary Emacs backup files; see Backup.) Commands like C-x v = and C-x v u make use of automatic version backups, if possible, to avoid having to access the network.

Setting vc-cvs-stay-local to nil disables the making of automatic version backups.

Automatic version backups have names of the form file.~version.~. This is similar to the name that C-x v ~ saves old versions to (see Old Revisions), except for the additional dot (‘.’) after the version. The relevant VC commands can use both kinds of version backups. The main difference is that the manual version backups made by C-x v ~ are not deleted automatically when you commit.

CVS does not use locking by default, but there are ways to enable locking-like behavior using its CVSREAD or watch feature; see the CVS documentation for details. If that case, you can use C-x v v in Emacs to toggle locking, as you would for a locking-based version control system (see VC With A Locking VCS).