save-hooks.el

;;; SAVE-HOOKS --- Folder Actions on Save
;;
;; Author: Howard Abrams <howard.abrams@gmail.com>
;; Copyright © 2015, Howard Abrams, all rights reserved.
;; Created: 18 March 2015
;;
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;;
;;; Commentary:
;;
;;  A hook that analyzes the directory where a file is being saved and
;;  if there exists a file called .on-save, it executes it with the
;;  name of the file that was saved.
;;
;;  Note: The .on-save script must have the executable bit set, as
;;  well as a shebang line, since the hook simply calls it.
;;
;;  What good is this? Well, think of a script that kicks off the unit
;;  tests whenever a file is saved. Or how about a script with an
;;  rsync command to copy the file to a remote location.
;;
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;;
;;; Change log:
;;
;;   v1. Runs a script in the current directory of the file
;;   v2. Runs a script in an ancestor of the file's directory
;;
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;;
;; This program is free software; you can redistribute it and/or
;; modify it under the terms of the GNU General Public License as
;; published by the Free Software Foundation; either version 3, or
;; (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;; General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program; see the file COPYING.  If not, write to
;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth
;; Floor, Boston, MA 02110-1301, USA.
;;
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;;
;;; Code:

(defun parent-directory (dir)
  "Return the parent of DIR.  If dir is at the top of the tree, return nil."
  (unless (equal "/" dir)
    (file-name-directory (directory-file-name dir))))

(defun find-file-in-heirarchy (current-dir fname)
  "Search CURRENT-DIR for a file named FNAME, and walk up through the directory hierarchy."
  (let ((file (concat current-dir fname))
        (parent (parent-directory (expand-file-name current-dir))))
    (if (file-exists-p file)
        file
      (when parent
        (find-file-in-heirarchy parent fname)))))

(defun ha/find-on-save-script (filename)
  "Locate a .on-save script in directory containing FILENAME (or ancestor)."
  (let ((dir (file-name-directory filename)))
    (concat (find-file-in-heirarchy dir ".on-save") " " filename)))

(defun ha/folder-action-save-hook ()
  "A file save hook that will look for a script in the same directory, called .on-save.  It will then execute that script asynchronously."
  (let* ((filename (buffer-file-name))
         (script (ha/find-on-save-script filename)))
    (write-file filename nil)
    ;; Need to re-add the hook to the local file:
    (add-hook 'local-write-file-hooks 'ha/folder-action-save-hook)
    (when script
      (async-shell-command script))))

(add-hook 'local-write-file-hooks 'ha/folder-action-save-hook)

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;;; save-hooks.el ends here