git{,-blame}.el: remove old bitrotting Emacs code

The git-blame.el mode has been superseded by Emacs's own
vc-annotate (invoked by C-x v g). Users of the git.el mode are now
much better off using either Magit or the Git backend for Emacs's own
VC mode.

These modes were added over 10 years ago when Emacs's own Git support
was much less mature, and there weren't other mature modes in the wild
or shipped with Emacs itself.

These days these modes have few if any users, and users of git aren't
well served by us shipping these (some OS's install them alongside git
by default, which is confusing and leads users astray).

So let's remove these per Alexandre Julliard's message to the
ML[1]. If someone still wants these for some reason they're better
served by hosting these elsewhere (e.g. on ELPA), instead of us
distributing them with git.

However, since downstream packagers such as Debian are packaging this
as git-el it's less disruptive to still carry these files as Elisp
code that'll error out with a message suggesting alternatives, rather
than drop the files entirely[2].

Then rather than receive a cryptic load error when they upgrade
existing users will get an error directing them to the README file, or
to just stop requiring these modes. I think it makes sense to link to
GitHub's hosting of contrib/emacs/README (which'll be updated by the
time users see this) so they don't have to hunt down the packaged
README on their local system.

1. "Re: [PATCH] git.el: handle default excludesfile
   properly" (87muzlwhb0.fsf@winehq.org) --
   https://public-inbox.org/git/87muzlwhb0.fsf@winehq.org/

2. "Re: [PATCH v3] git{,-blame}.el: remove old bitrotting Emacs
   code" (20180327165751.GA4343@aiede.svl.corp.google.com) --
   https://public-inbox.org/git/20180327165751.GA4343@aiede.svl.corp.google.com/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 483 deletions

diff --git a/contrib/emacs/git-blame.el b/contrib/emacs/git-blame.el
index 510e0f7103..6a8a2b8ff1 100644
--- a/contrib/emacs/git-blame.el
+++ b/contrib/emacs/git-blame.el
@@ -1,483 +1,6 @@
-;;; git-blame.el --- Minor mode for incremental blame for Git  -*- coding: utf-8 -*-
-;;
-;; Copyright (C) 2007  David Kågedal
-;;
-;; Authors:    David Kågedal <davidk@lysator.liu.se>
-;; Created:    31 Jan 2007
-;; Message-ID: <87iren2vqx.fsf@morpheus.local>
-;; License:    GPL
-;; Keywords:   git, version control, release management
-;;
-;; Compatibility: Emacs21, Emacs22 and EmacsCVS
-;;                Git 1.5 and up
-
-;; This file is *NOT* part of GNU Emacs.
-;; This file is distributed under the same terms as GNU Emacs.
-
-;; 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 2 of
-;; the License, 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; if not, see
-;; <http://www.gnu.org/licenses/>.
-
-;; http://www.fsf.org/copyleft/gpl.html
-
-
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;;
-;;; Commentary:
-;;
-;; Here is an Emacs implementation of incremental git-blame.  When you
-;; turn it on while viewing a file, the editor buffer will be updated by
-;; setting the background of individual lines to a color that reflects
-;; which commit it comes from.  And when you move around the buffer, a
-;; one-line summary will be shown in the echo area.
-
-;;; Installation:
-;;
-;; To use this package, put it somewhere in `load-path' (or add
-;; directory with git-blame.el to `load-path'), and add the following
-;; line to your .emacs:
-;;
-;;    (require 'git-blame)
-;;
-;; If you do not want to load this package before it is necessary, you
-;; can make use of the `autoload' feature, e.g. by adding to your .emacs
-;; the following lines
-;;
-;;    (autoload 'git-blame-mode "git-blame"
-;;              "Minor mode for incremental blame for Git." t)
-;;
-;; Then first use of `M-x git-blame-mode' would load the package.
-
-;;; Compatibility:
-;;
-;; It requires GNU Emacs 21 or later and Git 1.5.0 and up
-;;
-;; If you'are using Emacs 20, try changing this:
-;;
-;;            (overlay-put ovl 'face (list :background
-;;                                         (cdr (assq 'color (cddddr info)))))
-;;
-;; to
-;;
-;;            (overlay-put ovl 'face (cons 'background-color
-;;                                         (cdr (assq 'color (cddddr info)))))
-
-
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;;
-;;; Code:
-
-(eval-when-compile (require 'cl))			      ; to use `push', `pop'
-(require 'format-spec)
-
-(defface git-blame-prefix-face
-  '((((background dark)) (:foreground "gray"
-                          :background "black"))
-    (((background light)) (:foreground "gray"
-                           :background "white"))
-    (t (:weight bold)))
-  "The face used for the hash prefix."
-  :group 'git-blame)
-
-(defgroup git-blame nil
-  "A minor mode showing Git blame information."
-  :group 'git
-  :link '(function-link git-blame-mode))
-
-
-(defcustom git-blame-use-colors t
-  "Use colors to indicate commits in `git-blame-mode'."
-  :type 'boolean
-  :group 'git-blame)
-
-(defcustom git-blame-prefix-format
-  "%h %20A:"
-  "The format of the prefix added to each line in `git-blame'
-mode. The format is passed to `format-spec' with the following format keys:
-
-  %h - the abbreviated hash
-  %H - the full hash
-  %a - the author name
-  %A - the author email
-  %c - the committer name
-  %C - the committer email
-  %s - the commit summary
-"
-  :group 'git-blame)
-
-(defcustom git-blame-mouseover-format
-  "%h %a %A: %s"
-  "The format of the description shown when pointing at a line in
-`git-blame' mode. The format string is passed to `format-spec'
-with the following format keys:
-
-  %h - the abbreviated hash
-  %H - the full hash
-  %a - the author name
-  %A - the author email
-  %c - the committer name
-  %C - the committer email
-  %s - the commit summary
-"
-  :group 'git-blame)
-
-
-(defun git-blame-color-scale (&rest elements)
-  "Given a list, returns a list of triples formed with each
-elements of the list.
-
-a b => bbb bba bab baa abb aba aaa aab"
-  (let (result)
-    (dolist (a elements)
-      (dolist (b elements)
-        (dolist (c elements)
-          (setq result (cons (format "#%s%s%s" a b c) result)))))
-    result))
-
-;; (git-blame-color-scale "0c" "04" "24" "1c" "2c" "34" "14" "3c") =>
-;; ("#3c3c3c" "#3c3c14" "#3c3c34" "#3c3c2c" "#3c3c1c" "#3c3c24"
-;; "#3c3c04" "#3c3c0c" "#3c143c" "#3c1414" "#3c1434" "#3c142c" ...)
-
-(defmacro git-blame-random-pop (l)
-  "Select a random element from L and returns it. Also remove
-selected element from l."
-  ;; only works on lists with unique elements
-  `(let ((e (elt ,l (random (length ,l)))))
-     (setq ,l (remove e ,l))
-     e))
-
-(defvar git-blame-log-oneline-format
-  "format:[%cr] %cn: %s"
-  "*Formatting option used for describing current line in the minibuffer.
-
-This option is used to pass to git log --pretty= command-line option,
-and describe which commit the current line was made.")
-
-(defvar git-blame-dark-colors
-  (git-blame-color-scale "0c" "04" "24" "1c" "2c" "34" "14" "3c")
-  "*List of colors (format #RGB) to use in a dark environment.
-
-To check out the list, evaluate (list-colors-display git-blame-dark-colors).")
-
-(defvar git-blame-light-colors
-  (git-blame-color-scale "c4" "d4" "cc" "dc" "f4" "e4" "fc" "ec")
-  "*List of colors (format #RGB) to use in a light environment.
-
-To check out the list, evaluate (list-colors-display git-blame-light-colors).")
-
-(defvar git-blame-colors '()
-  "Colors used by git-blame. The list is built once when activating git-blame
-minor mode.")
-
-(defvar git-blame-ancient-color "dark green"
-  "*Color to be used for ancient commit.")
-
-(defvar git-blame-autoupdate t
-  "*Automatically update the blame display while editing")
-
-(defvar git-blame-proc nil
-  "The running git-blame process")
-(make-variable-buffer-local 'git-blame-proc)
-
-(defvar git-blame-overlays nil
-  "The git-blame overlays used in the current buffer.")
-(make-variable-buffer-local 'git-blame-overlays)
-
-(defvar git-blame-cache nil
-  "A cache of git-blame information for the current buffer")
-(make-variable-buffer-local 'git-blame-cache)
-
-(defvar git-blame-idle-timer nil
-  "An idle timer that updates the blame")
-(make-variable-buffer-local 'git-blame-cache)
-
-(defvar git-blame-update-queue nil
-  "A queue of update requests")
-(make-variable-buffer-local 'git-blame-update-queue)
-
-;; FIXME: docstrings
-(defvar git-blame-file nil)
-(defvar git-blame-current nil)
-
-(defvar git-blame-mode nil)
-(make-variable-buffer-local 'git-blame-mode)
-
-(defvar git-blame-mode-line-string " blame"
-  "String to display on the mode line when git-blame is active.")
-
-(or (assq 'git-blame-mode minor-mode-alist)
-    (setq minor-mode-alist
-	  (cons '(git-blame-mode git-blame-mode-line-string) minor-mode-alist)))
-
-;;;###autoload
-(defun git-blame-mode (&optional arg)
-  "Toggle minor mode for displaying Git blame
-
-With prefix ARG, turn the mode on if ARG is positive."
-  (interactive "P")
-  (cond
-   ((null arg)
-    (if git-blame-mode (git-blame-mode-off) (git-blame-mode-on)))
-   ((> (prefix-numeric-value arg) 0) (git-blame-mode-on))
-   (t (git-blame-mode-off))))
-
-(defun git-blame-mode-on ()
-  "Turn on git-blame mode.
-
-See also function `git-blame-mode'."
-  (make-local-variable 'git-blame-colors)
-  (if git-blame-autoupdate
-      (add-hook 'after-change-functions 'git-blame-after-change nil t)
-    (remove-hook 'after-change-functions 'git-blame-after-change t))
-  (git-blame-cleanup)
-  (let ((bgmode (cdr (assoc 'background-mode (frame-parameters)))))
-    (if (eq bgmode 'dark)
-	(setq git-blame-colors git-blame-dark-colors)
-      (setq git-blame-colors git-blame-light-colors)))
-  (setq git-blame-cache (make-hash-table :test 'equal))
-  (setq git-blame-mode t)
-  (git-blame-run))
-
-(defun git-blame-mode-off ()
-  "Turn off git-blame mode.
-
-See also function `git-blame-mode'."
-  (git-blame-cleanup)
-  (if git-blame-idle-timer (cancel-timer git-blame-idle-timer))
-  (setq git-blame-mode nil))
-
-;;;###autoload
-(defun git-reblame ()
-  "Recalculate all blame information in the current buffer"
-  (interactive)
-  (unless git-blame-mode
-    (error "Git-blame is not active"))
-
-  (git-blame-cleanup)
-  (git-blame-run))
-
-(defun git-blame-run (&optional startline endline)
-  (if git-blame-proc
-      ;; Should maybe queue up a new run here
-      (message "Already running git blame")
-    (let ((display-buf (current-buffer))
-          (blame-buf (get-buffer-create
-                      (concat " git blame for " (buffer-name))))
-          (args '("--incremental" "--contents" "-")))
-      (if startline
-          (setq args (append args
-                             (list "-L" (format "%d,%d" startline endline)))))
-      (setq args (append args
-                         (list (file-name-nondirectory buffer-file-name))))
-      (setq git-blame-proc
-            (apply 'start-process
-                   "git-blame" blame-buf
-                   "git" "blame"
-                   args))
-      (with-current-buffer blame-buf
-        (erase-buffer)
-        (make-local-variable 'git-blame-file)
-        (make-local-variable 'git-blame-current)
-        (setq git-blame-file display-buf)
-        (setq git-blame-current nil))
-      (set-process-filter git-blame-proc 'git-blame-filter)
-      (set-process-sentinel git-blame-proc 'git-blame-sentinel)
-      (process-send-region git-blame-proc (point-min) (point-max))
-      (process-send-eof git-blame-proc))))
-
-(defun remove-git-blame-text-properties (start end)
-  (let ((modified (buffer-modified-p))
-        (inhibit-read-only t))
-    (remove-text-properties start end '(point-entered nil))
-    (set-buffer-modified-p modified)))
-
-(defun git-blame-cleanup ()
-  "Remove all blame properties"
-    (mapc 'delete-overlay git-blame-overlays)
-    (setq git-blame-overlays nil)
-    (remove-git-blame-text-properties (point-min) (point-max)))
-
-(defun git-blame-update-region (start end)
-  "Rerun blame to get updates between START and END"
-  (let ((overlays (overlays-in start end)))
-    (while overlays
-      (let ((overlay (pop overlays)))
-        (if (< (overlay-start overlay) start)
-            (setq start (overlay-start overlay)))
-        (if (> (overlay-end overlay) end)
-            (setq end (overlay-end overlay)))
-        (setq git-blame-overlays (delete overlay git-blame-overlays))
-        (delete-overlay overlay))))
-  (remove-git-blame-text-properties start end)
-  ;; We can be sure that start and end are at line breaks
-  (git-blame-run (1+ (count-lines (point-min) start))
-                 (count-lines (point-min) end)))
-
-(defun git-blame-sentinel (proc status)
-  (with-current-buffer (process-buffer proc)
-    (with-current-buffer git-blame-file
-      (setq git-blame-proc nil)
-      (if git-blame-update-queue
-          (git-blame-delayed-update))))
-  ;;(kill-buffer (process-buffer proc))
-  ;;(message "git blame finished")
-  )
-
-(defvar in-blame-filter nil)
-
-(defun git-blame-filter (proc str)
-  (with-current-buffer (process-buffer proc)
-    (save-excursion
-      (goto-char (process-mark proc))
-      (insert-before-markers str)
-      (goto-char (point-min))
-      (unless in-blame-filter
-        (let ((more t)
-              (in-blame-filter t))
-          (while more
-            (setq more (git-blame-parse))))))))
-
-(defun git-blame-parse ()
-  (cond ((looking-at "\\([0-9a-f]\\{40\\}\\) \\([0-9]+\\) \\([0-9]+\\) \\([0-9]+\\)\n")
-         (let ((hash (match-string 1))
-               (src-line (string-to-number (match-string 2)))
-               (res-line (string-to-number (match-string 3)))
-               (num-lines (string-to-number (match-string 4))))
-           (delete-region (point) (match-end 0))
-           (setq git-blame-current (list (git-blame-new-commit hash)
-                                         src-line res-line num-lines)))
-         t)
-        ((looking-at "\\([a-z-]+\\) \\(.+\\)\n")
-         (let ((key (match-string 1))
-               (value (match-string 2)))
-           (delete-region (point) (match-end 0))
-           (git-blame-add-info (car git-blame-current) key value)
-           (when (string= key "filename")
-             (git-blame-create-overlay (car git-blame-current)
-                                       (caddr git-blame-current)
-                                       (cadddr git-blame-current))
-             (setq git-blame-current nil)))
-         t)
-        (t
-         nil)))
-
-(defun git-blame-new-commit (hash)
-  (with-current-buffer git-blame-file
-    (or (gethash hash git-blame-cache)
-        ;; Assign a random color to each new commit info
-        ;; Take care not to select the same color multiple times
-        (let* ((color (if git-blame-colors
-                          (git-blame-random-pop git-blame-colors)
-                        git-blame-ancient-color))
-               (info `(,hash (color . ,color))))
-          (puthash hash info git-blame-cache)
-          info))))
-
-(defun git-blame-create-overlay (info start-line num-lines)
-  (with-current-buffer git-blame-file
-    (save-excursion
-      (let ((inhibit-point-motion-hooks t)
-            (inhibit-modification-hooks t))
-        (goto-char (point-min))
-        (forward-line (1- start-line))
-        (let* ((start (point))
-               (end (progn (forward-line num-lines) (point)))
-               (ovl (make-overlay start end))
-               (hash (car info))
-               (spec `((?h . ,(substring hash 0 6))
-                       (?H . ,hash)
-                       (?a . ,(git-blame-get-info info 'author))
-                       (?A . ,(git-blame-get-info info 'author-mail))
-                       (?c . ,(git-blame-get-info info 'committer))
-                       (?C . ,(git-blame-get-info info 'committer-mail))
-                       (?s . ,(git-blame-get-info info 'summary)))))
-          (push ovl git-blame-overlays)
-          (overlay-put ovl 'git-blame info)
-          (overlay-put ovl 'help-echo
-                       (format-spec git-blame-mouseover-format spec))
-          (if git-blame-use-colors
-              (overlay-put ovl 'face (list :background
-                                           (cdr (assq 'color (cdr info))))))
-          (overlay-put ovl 'line-prefix
-                       (propertize (format-spec git-blame-prefix-format spec)
-                                   'face 'git-blame-prefix-face)))))))
-
-(defun git-blame-add-info (info key value)
-  (nconc info (list (cons (intern key) value))))
-
-(defun git-blame-get-info (info key)
-  (cdr (assq key (cdr info))))
-
-(defun git-blame-current-commit ()
-  (let ((info (get-char-property (point) 'git-blame)))
-    (if info
-        (car info)
-      (error "No commit info"))))
-
-(defun git-describe-commit (hash)
-  (with-temp-buffer
-    (call-process "git" nil t nil
-                  "log" "-1"
-		  (concat "--pretty=" git-blame-log-oneline-format)
-                  hash)
-    (buffer-substring (point-min) (point-max))))
-
-(defvar git-blame-last-identification nil)
-(make-variable-buffer-local 'git-blame-last-identification)
-(defun git-blame-identify (&optional hash)
-  (interactive)
-  (let ((info (gethash (or hash (git-blame-current-commit)) git-blame-cache)))
-    (when (and info (not (eq info git-blame-last-identification)))
-      (message "%s" (nth 4 info))
-      (setq git-blame-last-identification info))))
-
-;; (defun git-blame-after-save ()
-;;   (when git-blame-mode
-;;     (git-blame-cleanup)
-;;     (git-blame-run)))
-;; (add-hook 'after-save-hook 'git-blame-after-save)
-
-(defun git-blame-after-change (start end length)
-  (when git-blame-mode
-    (git-blame-enq-update start end)))
-
-(defvar git-blame-last-update nil)
-(make-variable-buffer-local 'git-blame-last-update)
-(defun git-blame-enq-update (start end)
-  "Mark the region between START and END as needing blame update"
-  ;; Try to be smart and avoid multiple callouts for sequential
-  ;; editing
-  (cond ((and git-blame-last-update
-              (= start (cdr git-blame-last-update)))
-         (setcdr git-blame-last-update end))
-        ((and git-blame-last-update
-              (= end (car git-blame-last-update)))
-         (setcar git-blame-last-update start))
-        (t
-         (setq git-blame-last-update (cons start end))
-         (setq git-blame-update-queue (nconc git-blame-update-queue
-                                             (list git-blame-last-update)))))
-  (unless (or git-blame-proc git-blame-idle-timer)
-    (setq git-blame-idle-timer
-          (run-with-idle-timer 0.5 nil 'git-blame-delayed-update))))
-
-(defun git-blame-delayed-update ()
-  (setq git-blame-idle-timer nil)
-  (if git-blame-update-queue
-      (let ((first (pop git-blame-update-queue))
-            (inhibit-point-motion-hooks t))
-        (git-blame-update-region (car first) (cdr first)))))
-
-(provide 'git-blame)
-
-;;; git-blame.el ends here
+(error "git-blame.el no longer ships with git. It's recommended
+to replace its use with Emacs's own vc-annotate. See
+contrib/emacs/README in git's
+sources (https://github.com/git/git/blob/master/contrib/emacs/README)
+for more info on suggested alternatives and for why this
+happened.")