Correct license statement

README.md

@@ -1,6 +1,8 @@
 # async-backup
 <a href="https://liberapay.com/contrapunctus/donate"><img alt="Donate using Liberapay" src="https://img.shields.io/liberapay/receives/contrapunctus.svg?logo=liberapay"></a>
 
+[![MELPA](https://melpa.org/packages/async-backup-badge.svg)](https://melpa.org/#/async-backup)
+
 Emacs has a built-in backup system, but it does not backup on each
 save. It can be made to, but that makes saving really slow (and the
 UI unresponsive), especially for large files.
@@ -14,6 +16,6 @@ To enable for a specific file -
   `M-x add-file-local-variable RET eval RET (add-hook 'after-save-hook #'async-backup nil t) RET`
 
 # License
-Chronometrist is released under your choice of [Unlicense](https://unlicense.org/) or the [WTFPL](http://www.wtfpl.net/).
+`async-backup` is released under your choice of [Unlicense](https://unlicense.org/) or the [WTFPL](http://www.wtfpl.net/).
 
 (See files [UNLICENSE](UNLICENSE) and [WTFPL](WTFPL)).

async-backup.el

@@ -33,13 +33,15 @@
 
 ;;; Code:
 (require 'cl-lib)
+(eval-when-compile
+  (require 'subr-x))
 
 (defgroup async-backup nil
   "Backup on each save without freezing Emacs."
   :group 'files)
 
 (defcustom async-backup-location
-  (concat (locate-user-emacs-file "") "/async-backup")
+  (locate-user-emacs-file "async-backup")
   "Path to save backups to."
   :type 'directory)
 
@@ -50,20 +52,25 @@
 (defcustom async-backup-predicates '(identity)
   "List of predicates which must all pass for a file to be backup up.
 Each predicate must accept a single argemnt, which is the full
-path of the file to be backed up.")
+path of the file to be backed up."
+  :type '(repeat function))
 
-(defun async-backup ()
-  "Backup file visited by current buffer."
-  (let* ((backup-root    (string-remove-suffix "/" (expand-file-name async-backup-location)))
-         (input-file     (buffer-file-name))
-         (file-name-base (file-name-base input-file))
-         (file-extension (file-name-extension input-file))
-         (file-directory (file-name-directory input-file))
+;;;###autoload
+(defun async-backup (&optional file)
+  "Backup FILE, or file visited by current buffer."
+  (let* ((backup-root      (string-remove-suffix "/" (expand-file-name async-backup-location)))
+         (input-file       (if file (expand-file-name file)
+                             (buffer-file-name)))
+         (file-name-base   (file-name-base input-file))
+         (file-extension   (file-name-extension input-file))
+         (file-directory   (file-name-directory input-file))
          (output-directory (concat backup-root file-directory))
-         (output-file    (concat output-directory
-                                 file-name-base
-                                 "-" (format-time-string async-backup-time-format)
-                                 "." file-extension)))
+         (output-file      (concat output-directory
+                                   file-name-base
+                                   "-" (format-time-string async-backup-time-format)
+                                   (if file-extension
+                                       (concat "." file-extension)
+                                     ""))))
     (unless (file-exists-p output-directory)
       (make-directory output-directory t))
     (when (cl-every (lambda (predicate)