vc-tag-precondition

vc-tag-precondition is a compiled Lisp function in `vc.el'.

(vc-tag-precondition DIR)

Scan the tree below DIR, looking for files not up-to-date.
If any file is not up-to-date, return the name of the first such file.
(This means, neither tag creation nor retrieval is allowed.)
If one or more of the files are currently visited, return `visited'.
Otherwise, return nil.