cvs-mode-tag). It's usually preferable to tag a directory at a time. Rather than selecting all files (which too often doesn't select all files but only the few that are displayed), clear the selection with M-<DEL> (
cvs-mode-unmark-all-files), position the cursor on the directory you want to tag and hit t.
By default, ‘tag’ commands ignore the marks. This can be changed
cvs-invert-ignore-marks. Also, by default ‘tag’ can
only be applied to directories, see
cvs-force-dir-tag if you want
to change this behavior.