Ignore the minibuffer prompt.
From Milan Zamazal <Milan.Zamazal@qbizm.com>:
(file-cache-minibuffer-complete): Don't try to delete the minibuffer prompt.
(file-cache-minibuffer-complete): Use file-cache-assoc-function.
Use file-cache-case-fold-search variable
(file-cache-add-file): Use file-cache-assoc-function
(file-cache-delete-file): likewise
(file-cache-directory-name): likewise
(file-cache-debug-read-from-minibuffer): likewise
defaulting to the value of completion-ignore-case.
(file-cache-minibuffer-complete): Use it.
(file-cache-files-matching, file-cache-files-matching-internal):
New functions.
before adding it. Non-existing files are simply skipped.
(file-cache-add-directory): Checks to see if directory exists
before adding it. Non-existing directories are simply skipped.
