emacs: create patch filename from subject for inline patch fake parts

Use the mail subject line for creating a descriptive filename for the wash
generated inline patch fake parts. The names are similar to the ones
created by 'git format-patch'.

If the user has notmuch-wash-convert-inline-patch-to-part hook enabled in
notmuch-show-insert-text/plain-hook, this will change the old default
filename of "inline patch" in fake parts:

[ inline patch: inline patch (as text/x-diff) ]

into, for example:

[ 0002-emacs-create-patch-filename-from-subject-for-inline.patch: inline patch (as text/x-diff) ]

which is typically the same filename the sender had if he was using 'git
format-patch' and 'git send-email'.

Signed-off-by: Jani Nikula <jani@nikula.org>

1 files changed, 42 insertions, 1 deletions

diff --git a/emacs/notmuch-wash.el b/emacs/notmuch-wash.el
index e9f2dbad..5c1e8300 100644
--- a/emacs/notmuch-wash.el
+++ b/emacs/notmuch-wash.el
@@ -290,6 +290,44 @@ When doing so, maintaining citation leaders in the wrapped text."
 
 (defvar diff-file-header-re) ; From `diff-mode.el'.
 
+(defun notmuch-wash-subject-to-filename (subject &optional maxlen)
+  "Convert a mail SUBJECT into a filename.
+
+The resulting filename is similar to the names generated by \"git
+format-patch\", without the leading patch sequence number
+\"0001-\" and \".patch\" extension. Any leading \"[PREFIX]\"
+style strings are removed prior to conversion.
+
+Optional argument MAXLEN is the maximum length of the resulting
+filename, before trimming any trailing . and - characters."
+  (let* ((s (replace-regexp-in-string "^ *\\(\\[[^]]*\\] *\\)*" "" subject))
+	 (s (replace-regexp-in-string "[^A-Za-z0-9._]+" "-" s))
+	 (s (replace-regexp-in-string "\\.+" "." s))
+	 (s (if maxlen (substring s 0 (min (length s) maxlen)) s))
+	 (s (replace-regexp-in-string "[.-]*$" "" s)))
+    s))
+
+(defun notmuch-wash-subject-to-patch-sequence-number (subject)
+  "Convert a patch mail SUBJECT into a patch sequence number.
+
+Return the patch sequence number N from the last \"[PATCH N/M]\"
+style prefix in SUBJECT, or nil if such a prefix can't be found."
+  (when (string-match
+	 "^ *\\(\\[[^]]*\\] *\\)*\\[[^]]*?\\([0-9]+\\)/[0-9]+[^]]*\\].*"
+	 subject)
+      (string-to-number (substring subject (match-beginning 2) (match-end 2)))))
+
+(defun notmuch-wash-subject-to-patch-filename (subject)
+  "Convert a patch mail SUBJECT into a filename.
+
+The resulting filename is similar to the names generated by \"git
+format-patch\". If the patch mail was generated and sent using
+\"git format-patch/send-email\", this should re-create the
+original filename the sender had."
+  (format "%04d-%s.patch"
+	  (or (notmuch-wash-subject-to-patch-sequence-number subject) 1)
+	  (notmuch-wash-subject-to-filename subject 52)))
+
 (defun notmuch-wash-convert-inline-patch-to-part (msg depth)
   "Convert an inline patch into a fake 'text/x-diff' attachment.
 
@@ -316,7 +354,10 @@ for error."
 	    (setq part (plist-put part :content-type "inline-patch-fake-part"))
 	    (setq part (plist-put part :content (buffer-string)))
 	    (setq part (plist-put part :id -1))
-	    (setq part (plist-put part :filename "inline patch"))
+	    (setq part (plist-put part :filename
+				  (notmuch-wash-subject-to-patch-filename
+				   (plist-get
+				    (plist-get msg :headers) :Subject))))
 	    (delete-region (point-min) (point-max))
 	    (notmuch-show-insert-bodypart nil part depth))))))