mh-folder-completion-function

mh-folder-completion-function is an autoloaded Lisp function in `mh-utils.el'.

(mh-folder-completion-function NAME PREDICATE FLAG)

Programmable completion for folder names.
NAME is the partial folder name that has been input. PREDICATE if
non-nil is a function that is used to filter the possible
choices. FLAG is nil to indicate `try-completion', t for
`all-completions', or the symbol lambda for `test-completion'.
See Info node `(elisp) Programmed Completion' for details.