[PATCH] emacs: Add 'pretty-sha-path'.

[Alex Kost <alezost@gmail.com>]

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Hello,

Ludovic suggested to include “pretty-sha-path.el” in the repo, so here
is the patch for that.

Also I forgot to mention “emacs/guix-messages.el” in “emacs.am” in
commit 62f261d, so I did it in this patch (I hope it's not too evil :-))


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From e7ca6550d7f33d894e0023e3305938fce365fdba Mon Sep 17 00:00:00 2001
From: Alex Kost <alezost@gmail.com>
Date: Tue, 4 Nov 2014 19:38:27 +0300
Subject: [PATCH] emacs: Add 'pretty-sha-path'.

* emacs/pretty-sha-path.el: New file.
* emacs.am (ELFILES): Add it.
* doc/emacs.texi (Emacs Pretty Path): New node.
---
 doc/emacs.texi           |  41 ++++++++++
 emacs.am                 |   4 +-
 emacs/pretty-sha-path.el | 200 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 244 insertions(+), 1 deletion(-)
 create mode 100644 emacs/pretty-sha-path.el

diff --git a/doc/emacs.texi b/doc/emacs.texi
index 9e8fec4..427700e 100644
--- a/doc/emacs.texi
+++ b/doc/emacs.texi
@@ -18,6 +18,7 @@ guix package}).  Specifically, ``guix.el'' makes it easy to:
 * Initial Setup: Emacs Initial Setup.	Preparing @file{~/.emacs}.
 * Usage: Emacs Usage.			Using the interface.
 * Configuration: Emacs Configuration.	Configuring the interface.
+* Pretty SHA Path: Emacs Pretty Path.	Prettifying @file{/gnu/store/@dots{}} paths.
 @end menu
 
 @node Emacs Initial Setup
@@ -422,3 +423,43 @@ buffers.
 Various settings for ``info'' buffers.
 
 @end table
+
+
+@node Emacs Pretty Path
+@subsection Pretty SHA Path Mode
+
+Along with ``guix.el'', GNU@tie{}Guix comes with ``pretty-sha-path.el''.
+It provides a minor mode for abbreviating store paths by replacing
+SHA-sequences of symbols with ``@dots{}'':
+
+@example
+/gnu/store/onecansee32lettersandnumbershere-foo-0.1  @result{}  /gnu/store/…-foo-0.1
+@end example
+
+Once you set up ``guix.el'' (@pxref{Emacs Initial Setup}), the following
+commands become available:
+
+@table @kbd
+
+@item M-x pretty-sha-path-mode
+Enable/disable prettifying for the current buffer.
+
+@item M-x pretty-sha-path-global-mode
+Enable/disable prettifying globally.
+
+@end table
+
+To automatically enable @code{pretty-sha-path-mode} globally on Emacs
+start, add the following line to your init file:
+
+@example
+(pretty-sha-path-global-mode)
+@end example
+
+If you want to enable it only for specific major modes, add it to the
+mode hooks (@pxref{Hooks,,, emacs, The GNU Emacs Manual}), for example:
+
+@example
+(add-hook 'shell-mode-hook 'pretty-sha-path-mode)
+(add-hook 'dired-mode-hook 'pretty-sha-path-mode)
+@end example
diff --git a/emacs.am b/emacs.am
index 35470a3..dba0a0c 100644
--- a/emacs.am
+++ b/emacs.am
@@ -24,8 +24,10 @@ ELFILES =					\
   emacs/guix-history.el				\
   emacs/guix-info.el				\
   emacs/guix-list.el				\
+  emacs/guix-messages.el			\
   emacs/guix-utils.el				\
-  emacs/guix.el
+  emacs/guix.el					\
+  emacs/pretty-sha-path.el
 
 if HAVE_EMACS
 
diff --git a/emacs/pretty-sha-path.el b/emacs/pretty-sha-path.el
new file mode 100644
index 0000000..d991950
--- /dev/null
+++ b/emacs/pretty-sha-path.el
@@ -0,0 +1,200 @@
+;;; pretty-sha-path.el --- Prettify Guix store paths
+
+;; Copyright © 2014 Alex Kost <alezost@gmail.com>
+
+;; This file is part of GNU Guix.
+
+;; GNU Guix 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 of the License, or
+;; (at your option) any later version.
+
+;; GNU Guix 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.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This package provides minor-mode for prettifying Guix/Nix store
+;; paths, i.e. after enabling `pretty-sha-path-mode',
+;; '/gnu/store/herewehavefancylettersandnumbers-foo-0.1' paths will be
+;; replaced with '/gnu/store/…-foo-0.1' paths in the current buffer.
+;; There is also `pretty-sha-path-global-mode' for global prettifying.
+
+;; To install, add the following to your emacs init file:
+;;
+;;   (add-to-list 'load-path "/path/to/pretty-sha-path")
+;;   (autoload 'pretty-sha-path-mode "pretty-sha-path" nil t)
+;;   (autoload 'pretty-sha-path-global-mode "pretty-sha-path" nil t)
+
+;; If you want to enable/disable composition after "M-x font-lock-mode",
+;; use the following setting:
+;;
+;;   (setq font-lock-extra-managed-props
+;;         (cons 'composition font-lock-extra-managed-props))
+
+;; Credits:
+;;
+;; Thanks to Ludovic Courtès for the idea of this package.
+;;
+;; Thanks to the authors of `prettify-symbols-mode' (part of Emacs 24.4)
+;; and "pretty-symbols.el" <http://github.com/drothlis/pretty-symbols>
+;; for the code.  It helped to write this package.
+
+;;; Code:
+
+(defgroup pretty-sha-path nil
+  "Prettify Guix/Nix store paths."
+  :prefix "pretty-sha-path-"
+  :group 'font-lock
+  :group 'convenience)
+
+(defcustom pretty-sha-path-char ?…
+  "Character used for prettifying."
+  :type 'character
+  :group 'pretty-sha-path)
+
+(defcustom pretty-sha-path-decompose-force nil
+  "If non-nil, remove any composition.
+
+By default, after disabling `pretty-sha-path-mode',
+compositions (prettifying paths with `pretty-sha-path-char') are
+removed only from strings matching `pretty-sha-path-regexp', so
+that compositions created by other modes are left untouched.
+
+Set this variable to non-nil, if you want to remove any
+composition unconditionally (like `prettify-symbols-mode' does).
+Most likely it will do no harm and will make the process of
+disabling `pretty-sha-path-mode' a little faster."
+  :type 'boolean
+  :group 'pretty-sha-path)
+
+(defcustom pretty-sha-path-regexp
+  (rx "/"
+      (or "nix" "gnu")
+      "/store/"
+      (group (= 32 alnum)))
+  "Regexp matching SHA paths.
+
+Disable `pretty-sha-path-mode' before modifying this variable and
+make sure to modify `pretty-sha-path-regexp-group' if needed.
+
+Example of a \"deeper\" prettifying:
+
+  (setq pretty-sha-path-regexp \"store/[[:alnum:]]\\\\\\={32\\\\}\"
+        pretty-sha-path-regexp-group 0)
+
+This will transform
+'/gnu/store/onecansee32lettersandnumbershere-foo-0.1' into
+'/gnu/…-foo-0.1'"
+  :type 'regexp
+  :group 'pretty-sha-path)
+
+(defcustom pretty-sha-path-regexp-group 1
+  "Regexp group in `pretty-sha-path-regexp' for prettifying."
+  :type 'integer
+  :group 'pretty-sha-path)
+
+(defvar pretty-sha-path-special-modes
+  '(guix-info-mode ibuffer-mode)
+  "List of special modes that support font-locking.
+
+By default, \\[pretty-sha-path-global-mode] enables prettifying
+in all buffers except the ones where `font-lock-defaults' is
+nil (see Info node `(elisp) Font Lock Basics'), because it may
+break the existing highlighting.
+
+Modes from this list and all derived modes are exceptions
+\(`pretty-sha-path-global-mode' enables prettifying there).")
+
+(defvar pretty-sha-path-flush-function
+  (cond ((fboundp 'font-lock-flush) #'font-lock-flush)
+        ((fboundp 'jit-lock-refontify) #'jit-lock-refontify))
+  "Function used to refontify buffer.
+This function is called without arguments after
+enabling/disabling `pretty-sha-path-mode'.
+If nil, do nothing.")
+
+(defun pretty-sha-path-compose ()
+  "Compose matching region in the current buffer."
+  (let ((beg (match-beginning pretty-sha-path-regexp-group))
+        (end (match-end       pretty-sha-path-regexp-group)))
+    (compose-region beg end pretty-sha-path-char 'decompose-region))
+  ;; Return nil because we're not adding any face property.
+  nil)
+
+(defun pretty-sha-path-decompose-buffer ()
+  "Remove path compositions from the current buffer."
+  (with-silent-modifications
+    (let ((inhibit-read-only t))
+      (if pretty-sha-path-decompose-force
+          (remove-text-properties (point-min)
+                                  (point-max)
+                                  '(composition nil))
+        (save-excursion
+          (goto-char (point-min))
+          (while (re-search-forward pretty-sha-path-regexp nil t)
+            (remove-text-properties
+             (match-beginning pretty-sha-path-regexp-group)
+             (match-end       pretty-sha-path-regexp-group)
+             '(composition nil))))))))
+
+;;;###autoload
+(define-minor-mode pretty-sha-path-mode
+  "Toggle Pretty SHA Path mode.
+
+With a prefix argument ARG, enable Pretty SHA Path mode if ARG is
+positive, and disable it otherwise.  If called from Lisp, enable
+the mode if ARG is omitted or nil.
+
+When Pretty SHA Path mode is enabled, SHA-parts of the Guix/Nix
+store paths (see `pretty-sha-path-regexp') are prettified,
+i.e. displayed as `pretty-sha-path-char' character.  This mode
+can be enabled programmatically using hooks:
+
+  (add-hook 'shell-mode-hook 'pretty-sha-path-mode)
+
+It is possible to enable the mode in any buffer, however not any
+buffer's highlighting may survive after adding new elements to
+`font-lock-keywords' (see `pretty-sha-path-special-modes' for
+details).
+
+Also you can use `pretty-sha-path-global-mode' to enable Pretty
+SHA Path mode for all modes that support font-locking."
+  :init-value nil
+  :lighter " …"
+  (let ((keywords `((,pretty-sha-path-regexp
+                     (,pretty-sha-path-regexp-group
+                      (pretty-sha-path-compose))))))
+    (if pretty-sha-path-mode
+        ;; Turn on.
+        (font-lock-add-keywords nil keywords)
+      ;; Turn off.
+      (font-lock-remove-keywords nil keywords)
+      (pretty-sha-path-decompose-buffer))
+    (and pretty-sha-path-flush-function
+         (funcall pretty-sha-path-flush-function))))
+
+(defun pretty-sha-path-supported-p ()
+  "Return non-nil, if the mode can be harmlessly enabled in current buffer."
+  (or font-lock-defaults
+      (apply #'derived-mode-p pretty-sha-path-special-modes)))
+
+(defun pretty-sha-path-turn-on ()
+  "Enable `pretty-sha-path-mode' in the current buffer if needed.
+See `pretty-sha-path-special-modes' for details."
+  (and (not pretty-sha-path-mode)
+       (pretty-sha-path-supported-p)
+       (pretty-sha-path-mode)))
+
+;;;###autoload
+(define-globalized-minor-mode pretty-sha-path-global-mode
+  pretty-sha-path-mode pretty-sha-path-turn-on)
+
+(provide 'pretty-sha-path)
+
+;;; pretty-sha-path.el ends here
-- 
2.1.2