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+;;; gnus-article-treat-patch.el --- Highlight inline patches in articles
+;;
+;; Copyright © 2011-2019 Frank Terbeck <ft@bewatermyfriend.org>
+;;
+;; This file is not part of GNU Emacs.
+;;
+;; This file 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 Soft-
+;; ware Foundation; either version 3, or (at your option) any later version.
+;;
+;; This file 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 file. If not, see <http://www.gnu.org/licenses/>.
+;;
+;;
+;;; Commentary:
+;;
+;; Gnus addon to beautify patch-like emails. This uses a "ft/" prefix for
+;; everything to avoid clashing with anything upstream. That prefix can be
+;; savely s,ft/,,'d - if this is to be submitted to the gnus developers.
+
+(require 'diff-mode)
+
+(add-hook 'gnus-part-display-hook 'ft/gnus-article-treat-patch)
+
+;; Colour handling and faces
+(defun ft/gnus-colour-line (use-face)
+ "Set text overlay to `use-face' for the current line."
+ (overlay-put (make-overlay (point-at-bol) (point-at-eol)) 'face use-face))
+
+(make-face 'ft/gnus-three-dashes)
+(set-face-attribute 'ft/gnus-three-dashes nil :foreground "brightblue")
+(make-face 'ft/gnus-scissors)
+(set-face-attribute 'ft/gnus-scissors nil :foreground "brown")
+(make-face 'ft/gnus-diff-index)
+(set-face-attribute 'ft/gnus-diff-index nil :foreground "brightmagenta")
+(make-face 'ft/gnus-diff-hunk)
+(set-face-attribute 'ft/gnus-diff-hunk nil :foreground "brightblue")
+(make-face 'ft/gnus-diff-equals)
+(set-face-attribute 'ft/gnus-diff-equals nil :foreground "brightmagenta")
+(make-face 'ft/gnus-commit-message)
+(set-face-attribute 'ft/gnus-commit-message nil :foreground "white")
+(make-face 'ft/gnus-diff-stat-file)
+(set-face-attribute 'ft/gnus-diff-stat-file nil :foreground "yellow")
+(make-face 'ft/gnus-diff-stat-bar)
+(set-face-attribute 'ft/gnus-diff-stat-bar nil :foreground "magenta")
+(make-face 'ft/gnus-diff-stat-num)
+(set-face-attribute 'ft/gnus-diff-stat-num nil :foreground "white")
+(make-face 'ft/gnus-diff-misc)
+(set-face-attribute 'ft/gnus-diff-misc nil :foreground "magenta")
+(make-face 'ft/gnus-commit-comment)
+(set-face-attribute 'ft/gnus-commit-comment nil :inherit 'default)
+(make-face 'ft/gnus-diff-header)
+(set-face-attribute 'ft/gnus-diff-header nil :inherit 'diff-header)
+(make-face 'ft/gnus-diff-add)
+(set-face-attribute 'ft/gnus-diff-add nil :inherit 'diff-added)
+(make-face 'ft/gnus-diff-remove)
+(set-face-attribute 'ft/gnus-diff-remove nil :inherit 'diff-removed)
+
+;; Pseudo-headers
+(defvar ft/gnus-article-patch-pseudo-headers
+ '(("^Acked-by: " 'gnus-header-name 'gnus-header-from)
+ ("^C\\(c\\|C\\): " 'gnus-header-name 'gnus-header-from)
+ ("^From: " 'gnus-header-name 'gnus-header-from)
+ ("^Link: " 'gnus-header-name 'gnus-header-from)
+ ("^Reported-by: " 'gnus-header-name 'gnus-header-from)
+ ("^Reviewed-by: " 'gnus-header-name 'gnus-header-from)
+ ("^Signed-off-by: " 'gnus-header-name 'gnus-header-from)
+ ("^Subject: " 'gnus-header-name 'gnus-header-from)
+ ("^Suggested-by: " 'gnus-header-name 'gnus-header-from))
+ "List of lists of regular expressions (with two face names)
+which are used to determine the highlighting of pseudo headers in
+the commit message (such as \"Signed-off-by:\").
+
+The first face if used to highlight the header's name; the second
+highlights the header's value.")
+
+(defun ft/gnus-pseudo-header-get (line)
+ "Check if `line' is a pseudo header, and if so return its enty in
+`ft/gnus-article-patch-pseudo-headers'."
+ (catch 'done
+ (dolist (entry ft/gnus-article-patch-pseudo-headers)
+ (let ((regex (car entry)))
+ (if (string-match regex line)
+ (throw 'done entry))))
+ (throw 'done '())))
+
+(defun ft/gnus-pseudo-header-p (line)
+ "Returns `t' if `line' looks like a pseudo-header; `nil' otherwise.
+
+`ft/gnus-article-patch-pseudo-headers' is used to determine what a pseudo-header
+is."
+ (if (eq (ft/gnus-pseudo-header-get line) '()) nil t))
+
+(defun ft/gnus-pseudo-header-colour (line)
+ "Colourise a pseudo-header line."
+ (let ((data (ft/gnus-pseudo-header-get line)))
+ (if (eq data '())
+ nil
+ (let* ((s (point-at-bol))
+ (e (point-at-eol))
+ (colon (re-search-forward ":"))
+ (value (+ colon 1)))
+ (overlay-put (make-overlay s colon) 'face (nth 1 data))
+ (overlay-put (make-overlay value e) 'face (nth 2 data))))))
+
+;; diff-stat
+(defun ft/gnus-diff-stat-colour (line)
+ "Colourise a diff-stat line."
+ (let ((s (point-at-bol))
+ (e (point-at-eol))
+ (bar (- (re-search-forward "|") 1))
+ (num (- (re-search-forward "[0-9]") 1))
+ (pm (- (re-search-forward "\\([+-]\\|$\\)") 1)))
+
+ (overlay-put (make-overlay s (- bar 1)) 'face 'ft/gnus-diff-stat-file)
+ (overlay-put (make-overlay bar (+ bar 1)) 'face 'ft/gnus-diff-stat-bar)
+ (overlay-put (make-overlay num pm) 'face 'ft/gnus-diff-stat-num)
+
+ (goto-char pm)
+ (let* ((plus (looking-at "\\+"))
+ (regex (if plus "-+" "\\++"))
+ (brk (if plus
+ (re-search-forward "-" e t)
+ (re-search-forward "\\+" e t)))
+ (first-face (if plus 'ft/gnus-diff-add 'ft/gnus-diff-remove))
+ (second-face (if plus 'ft/gnus-diff-remove 'ft/gnus-diff-add)))
+
+ (if (eq brk nil)
+ (overlay-put (make-overlay pm e) 'face first-face)
+ (progn
+ (setq brk (- brk 1))
+ (overlay-put (make-overlay pm brk) 'face first-face)
+ (overlay-put (make-overlay brk e) 'face second-face))))))
+
+(defun ft/gnus-diff-stat-summary-colour (line)
+ "Colourise a diff-stat summary-line."
+ (let* ((e (point-at-eol))
+ (plus (- (re-search-forward "(\\+)" e t) 2))
+ (minus (- (re-search-forward "(-)" e t) 2)))
+ (overlay-put (make-overlay plus (+ plus 1)) 'face 'ft/gnus-diff-add)
+ (overlay-put (make-overlay minus (+ minus 1)) 'face 'ft/gnus-diff-remove)))
+
+(defun ft/gnus-diff-stat-line-p (line)
+ "Return `t' if `line' is a diff-stat line; `nil' otherwise."
+ (string-match "^ *[^ ]+[^|]+| +[0-9]+\\( *\\| +[+-]+\\)$" line))
+
+(defun ft/gnus-diff-stat-summary-p (line)
+ "Return `t' if `line' is a diff-stat summary-line; `nil' otherwise."
+ (string-match "^ *[0-9]+ file\\(s\\|\\) changed,.*insertion.*deletion" line))
+
+;; unified-diffs
+(defun ft/gnus-diff-header-p (line)
+ "Returns `t' if `line' looks like a diff-header; `nil' otherwise."
+ (cond
+ ((string-match "^\\(\\+\\+\\+\\|---\\) " line) t)
+ ((string-match "^diff -" line) t)
+ (t nil)))
+
+(defun ft/gnus-index-line-p (line)
+ "Returns `t' if `line' looks like an index-line; `nil' otherwise."
+ (cond
+ ((string-match "^Index: " line) t)
+ ((string-match "^index [0-9a-f]+\\.\\.[0-9a-f]+" line) t)
+ (t nil)))
+
+(defun ft/gnus-hunk-line-p (line)
+ "Returns `t' if `line' looks like a hunk-line; `nil' otherwise."
+ (string-match "^@@ -[0-9]+,[0-9]+ \\+[0-9]+,[0-9]+ @@" line))
+
+(defun ft/gnus-atp-misc-diff-p (line)
+ "Return `t' if `line' is a \"misc line\" with respect to patch
+treatment; `nil' otherwise."
+ (let ((patterns '("^new file"
+ "^RCS file:"
+ "^retrieving revision ")))
+ (catch 'done
+ (dolist (regex patterns)
+ (if (string-match regex line)
+ (throw 'done t)))
+ (throw 'done nil))))
+
+(defun ft/gnus-atp-looks-like-diff (line)
+ "Return `t' if `line' looks remotely like a line from a unified
+diff; `nil' otherwise."
+ (or (ft/gnus-index-line-p line)
+ (ft/gnus-diff-header-p line)
+ (ft/gnus-hunk-line-p line)))
+
+;; miscellaneous line handlers
+(defun ft/gnus-scissors-line-p (line)
+ "Returns `t' if `line' looks like a scissors-line; `nil' otherwise."
+ (cond
+ ((string-match "^\\( *--* *\\(8<\\|>8\\)\\)+ *-* *$" line) t)
+ (t nil)))
+
+;; Patch mail detection
+(defvar ft/gnus-article-patch-conditions nil
+ "List of conditions that will enable patch treatment. String
+values will be matched as regular expressions within the currently
+processed part. Non-string value are supposed to be code fragments,
+which determine whether or not to do treatment: The code needs to
+return `t' if treatment is wanted.")
+
+(defun ft/gnus-part-want-patch-treatment ()
+ "Run through `ft/gnus-article-patch-conditions' to determine whether
+patch treatment is wanted or not. Return `t' or `nil' accordingly."
+ (catch 'done
+ (dolist (entry ft/gnus-article-patch-conditions)
+ (cond
+ ((stringp entry)
+ (if (re-search-forward entry nil t)
+ (throw 'done t)))
+ (t
+ (if (eval entry)
+ (throw 'done t)))))
+ (throw 'done nil)))
+
+
+;; The actual article treatment code
+(defun ft/gnus-article-treat-patch-state-machine ()
+ "Implement the state machine which colourises a part of an article
+if it looks patch-like.
+
+The state machine works like this:
+
+ 0a. The machinery starts at the first line of the article's body. Not
+ the header lines. We don't care about header lines at all.
+
+ 0b. The whole thing works line by line. It doesn't do any forward or
+ backward looks.
+
+ 1. Initially, we assume, that what we'll see first is part of the
+ patch's commit-message. Hence this first initial state is
+ \"commit-message\". There are several ways out of this state:
+
+ a) a scissors line is found (see 2.)
+ b) a pseudo-header line is found (see 3.)
+ c) a three-dashes line is found (see 4.)
+ d) something that looks like the start of a unified diff is
+ found (see 7.)
+
+ 2. A scissors line is something that looks like a pair of scissors running
+ through a piece of paper. Like this:
+
+ ------ 8< ----- 8< ------
+
+ or this:
+
+ ------------>8-----------
+
+ The function `ft/gnus-scissors-line-p' decides whether a line is a
+ scissors line or not. After a scissors line was treated, the machine
+ will switch back to the \"commit-mesage\" state.
+
+ 3. This is very similar to a scissors line. It'll just return to the old
+ state after its being done. The `ft/gnus-pseudo-header-p' function
+ decides if a line is a pseudo header. The line will be appropriately
+ coloured.
+
+ 4. A three-dashes line is a line that looks like this: \"---\". It's the
+ definite end of the \"commit-message\" state. The three dashes line is
+ coloured and the state switches to \"commit-comment\". (See 5.)
+
+ 5. Nothing in \"commit-comment\" will appear in the generated commit (this
+ is git-am specific semantics, but it's useful, so...). It may contain
+ things like random comments or - promimently - a diff stat. (See 6.)
+
+ 6. A diff stat provides statistics about how much changed in a given commit
+ by files and by whole commit (in a summary line). Two functions
+ `ft/gnus-diff-stat-line-p' and `ft/gnus-diff-stat-summary-p' decide if a
+ line belongs to a diff stat. It's coloured appropriately and the state
+ switches back to \"commit-comment\".
+
+ 7. There is a function `ft/gnus-unified-diff-line-p' which will cause the
+ state to switch to \"unified-diff\" state from either \"commit-message\"
+ or \"commit-comment\". In this mode there can be a set of lines types:
+
+ a) diff-header lines (`ft/gnus-diff-header-p')
+ b) index lines (`ft/gnus-index-line-p')
+ c) hunk lines (`ft/gnus-hunk-line-p')
+ d) equals line (\"^==*$\")
+ e) context lines (\"^ \")
+ f) add lines (\"^\\+\")
+ g) remove lines (\"^-\")
+ h) empty lines (\"^$\")
+
+ This state runs until the end of the part."
+ (catch 'ft/gnus-atp-done
+ (let ((state 'commit-message)
+ line do-not-move)
+
+ (while t
+ ;; Put the current line into an easy-to-handle string variable.
+ (setq line
+ (buffer-substring-no-properties (point-at-bol) (point-at-eol)))
+ (setq do-not-move nil)
+
+ ;; Switched state machine. The "real" states are `commit-message',
+ ;; `commit-comment' and `unified-diff'. The other "states" are only
+ ;; single-line colourisations that return to their respective parent-
+ ;; state. Each state may (throw 'ft/gnus-atp-done) to leave the state-
+ ;; machine immediately.
+ (setq state
+ (cond
+
+ ((eq state 'commit-message)
+ (cond
+ ((ft/gnus-scissors-line-p line)
+ (ft/gnus-colour-line 'ft/gnus-scissors)
+ 'commit-message)
+ ((ft/gnus-pseudo-header-p line)
+ (ft/gnus-pseudo-header-colour line)
+ 'commit-message)
+ ((string= line "---")
+ (ft/gnus-colour-line 'ft/gnus-three-dashes)
+ 'commit-comment)
+ ((ft/gnus-atp-looks-like-diff line)
+ (setq do-not-move t)
+ 'unified-diff)
+ (t
+ (ft/gnus-colour-line 'ft/gnus-commit-message)
+ 'commit-message)))
+
+ ((eq state 'commit-comment)
+ (cond
+ ((ft/gnus-diff-stat-line-p line)
+ (ft/gnus-diff-stat-colour line)
+ 'commit-comment)
+ ((ft/gnus-diff-stat-summary-p line)
+ (ft/gnus-diff-stat-summary-colour line)
+ 'commit-comment)
+ ((ft/gnus-atp-looks-like-diff line)
+ (setq do-not-move t)
+ 'unified-diff)
+ (t
+ (ft/gnus-colour-line 'ft/gnus-commit-comment)
+ 'commit-comment)))
+
+ ((eq state 'unified-diff)
+ (cond
+ ((ft/gnus-diff-header-p line)
+ (ft/gnus-colour-line 'ft/gnus-diff-header)
+ 'unified-diff)
+ ((ft/gnus-index-line-p line)
+ (ft/gnus-colour-line 'ft/gnus-diff-index)
+ 'unified-diff)
+ ((ft/gnus-hunk-line-p line)
+ (ft/gnus-colour-line 'ft/gnus-diff-hunk)
+ 'unified-diff)
+ ((string-match "^==*$" line)
+ (ft/gnus-colour-line 'ft/gnus-diff-equals)
+ 'unified-diff)
+ ((string-match "^$" line)
+ 'unified-diff)
+ ((string-match "^ " line)
+ (ft/gnus-colour-line 'ft/gnus-diff-context)
+ 'unified-diff)
+ ((ft/gnus-atp-misc-diff-p line)
+ (ft/gnus-colour-line 'ft/gnus-diff-misc)
+ 'unified-diff)
+ ((string-match "^\\+" line)
+ (ft/gnus-colour-line 'ft/gnus-diff-add)
+ 'unified-diff)
+ ((string-match "^-" line)
+ (ft/gnus-colour-line 'ft/gnus-diff-remove)
+ 'unified-diff)
+ (t 'unified-diff)))))
+
+ (if (not do-not-move)
+ (if (> (forward-line) 0)
+ (throw 'ft/gnus-atp-done t)))))))
+
+(defun ft/gnus-article-treat-patch ()
+ "Highlight mail parts, that look like patches (well, usually
+they *are* patches - or possibly, when you take git's format-patch output,
+entire commit exports - including comments). This treatment assumes the
+use of unified diffs. Here is how it works:
+
+The most fancy type of patch mails look like this:
+
+ From: ...
+ Subject: ...
+ Other-Headers: ...
+
+ Body text, which can be reflecting the commit message but may
+ optionally be followed by a so called scissors line, which
+ looks like this (in case of a scissors line, the text above is
+ not part of the commit message):
+
+ -------8<----------
+
+ If there really was a scissors line, then it's usually
+ followed by repeated mail-headers. Which do not *have* to
+ be the same as the one from the sender.
+
+ From: ...
+ Subject: ...
+
+ More text. Usually part of the commit message. Likely
+ multiline. What follows may be an optional diffstat. If
+ there is one, it's usually preceded by a line that contains
+ only three dashes and nothing more. Before the diffstat,
+ however, there may be a set of pseudo headers again, like
+ these:
+
+ Acked-by: Mike Dev <md@other.tld>
+ Signed-off-by: Joe D. User <jdu@example.com>
+
+ ---
+ ChangeLog | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletions(-)
+
+ Now, there is again room for optional text, which is not
+ part of the actual commit message. May be multiline. Actually,
+ anything between the three-dashes line and the diff content
+ is ignored as far as the commit message goes.
+
+ Now for the actual diff part. I want this to work for as
+ many unified diff formats as possible. What comes to mind
+ is the format used by git and the format used by cvs and
+ quilt.
+
+ CVS style looks like this:
+
+ Index: foo/bar.c
+ ============================================================
+ --- boo.orig/foo/bar.c 2010-02-24 ....
+ +++ boo/foo/bar.c 2010-02-28 ....
+ @@ -1823,7 +1823,7 @@
+ <hunk>
+
+ There may be multiple hunks. Each file gets an \"Index:\" and
+ equals line. Now the git format looks like this:
+
+ diff --git a/ChangeLog b/ChangeLog
+ index 6ffbc8c..36e5c17 100644
+ --- a/ChangeLog
+ +++ b/ChangeLog
+ @@ -3,6 +3,9 @@
+ <hunk>
+
+ Again, there may be multiple hunks.
+
+ When all hunks and all files are done, there may be additional
+ text below the actual text.
+
+And that's it.
+
+You may define the look of several things: pseudo headers, scissor
+lines, three-dashes-line, equals lines, diffstat lines, diffstat
+summary. Then there is added lines, removed lines, context lines,
+diff-header lines and diff-file-header lines, for which we are
+borrowing the highlighting faces for from `diff-mode'."
+ (if (ft/gnus-part-want-patch-treatment)
+ (save-excursion
+ (progn
+ (let ((inhibit-read-only t))
+ (goto-char (point-min))
+ (ft/gnus-article-treat-patch-state-machine))))))
+
+(provide 'gnus-article-treat-patch)
generated by cgit v1.2.3-60-g2f50 (git 2.42.0) at 2024-10-18 21:28:57 +0000