Gnus is awesome

Gnus is my mail client. It's my NNTP and feed-reading client too. Gnus runs inside Emacs and is fancier than a Swiss Army knife. Here's a quick example.

Messages sent to the Puppet bugs list don't thread well. Redmine puts the bug's status in the middle of the subject. For example, this is the subject for a newly submitted bug:

• [Puppet - Bug #1686] (Unreviewed) Class names containing '-' cannot be used to scope variables

The next message about this bug has this subject:

• [Puppet - Bug #1686] (Needs design decision) Class names containing '-' cannot be used to scope variables

The stuff in parentheses prevents these two messages from displaying as part of the same thread. Of course I want threading so I can read all related messages at the same time and easily skip over bugs that I don't care about.

Gnus to the rescue! 8 lines of elisp gets me the threading I want. The hardest part is the regexp. Here's the code:

(defun map-alter-message-id (header)
(let ((subject (mail-header-subject header)))
(when (string-match "^\\(.*\\) \\(([^)]*)\\) \\(.*\\)$" subject)
  (setq map-temp header)
  (mail-header-set-subject
   header
   (concat (match-string 1 subject) " " (match-string 3 subject))))))
(setq gnus-alter-header-function 'map-alter-message-id)

This takes me from these 20 lines of unthreaded subjects:

• [Puppet - Bug #1686] (Unreviewed) Class names containing '-' cannot be used to scope variables
• [Puppet - Bug #1679] Control characters can't be used within a file resource
• [Puppet - Bug #1687] (Unreviewed) SELinux operations don't appear to be working on RHEL4
• [Puppet - Bug #1687] (Accepted) SELinux operations don't appear to be working on RHEL4
• [Puppet - Bug #1688] (Unreviewed) puppetca can't clean unsigned certs
• [Puppet - Bug #1688] (Accepted) puppetca can't clean unsigned certs
• [Puppet - Bug #1680] (Accepted) Setting user password on Solaris does not work
• [Puppet - Bug #1689] (Unreviewed) Hundreds of log messages a second because of dns resolution
• [Puppet - Bug #1690] (Unreviewed) Dependencies for class not preserved
• [Puppet - Bug #1690] (Rejected) Dependencies for class not preserved
• [Puppet - Bug #1686] (Needs design decision) Class names containing '-' cannot be used to scope variables
• [Puppet - Bug #1683] (Needs more information) "Random" errors coming from puppetmasterd
• [Puppet - Bug #1691] (Unreviewed) Realization fails if variable is used to represent array
• [Puppet - Bug #1691] Realization fails if variable is used to represent array
• [Puppet - Bug #1691] Realization fails if variable is used to represent array OR multiple realizes exist in a single 'if' statement
• [Puppet - Bug #1692] (Unreviewed) k5login fails to set mode when file is created
• [Puppet - Bug #1692] (Accepted) k5login fails to set mode when file is created
• [Puppet - Refactor #1693] (Accepted) All mentions of EPM should be removed from Rakefile and build library
• [Puppet - Refactor #1693] (Ready for Checkin) All mentions of EPM should be removed from Rakefile and build library

To just 8 after threading:

• [Puppet - Bug #1686] Class names containing '-' cannot be used to scope variables...
• [Puppet - Bug #1679] Control characters can't be used within a file resource...
• [Puppet - Bug #1687] SELinux operations don't appear to be working on RHEL4...
• [Puppet - Bug #1688] puppetca can't clean unsigned certs...
• [Puppet - Bug #1680] Setting user password on Solaris does not work...
• [Puppet - Bug #1689] Hundreds of log messages a second because of dns resolution...
• [Puppet - Bug #1690] Dependencies for class not preserved...
• [Puppet - Bug #1683] "Random" errors coming from puppetmasterd...

Many thanks to Larsi for Gnus and for Gmane too!