[VM] A few tricks with summary lines

[Uday Reddy]

Here are a couple of tricks for playing with summary lines, which might help
other people in managing their email with similar issues.

You might have noticed that VM has two variables

    vm-subject-ignored-prefix
    vm-subject-ignored-suffix

These are meant for stripping out prefixes like "Re: " and suffixes like
"(fwd)" that various mail clients add to the subject line.  It is the
stripped-out subject string that is used for things like sorting, threading,
making search folders etc.

Here is a somewhat unusual application of these features.  I participate in
various research-y discussions on StackExchange and subscribe to some topics
so that I am alerted whenever there is a new question or answer posted.
Unfortunately, StackExchange sends out a summary of posts on a daily basis.
(They don't have anything less frequent.)  Once I have subscribed to some 10
topics, my mail box was getting swamped with these alerts.  Each alert
message has a subject line like so:

  New category-theory questions for Sep 16 - Stack Exchange

So, I thought, why don't I strip out the suffix 

  "for Sep 16 - StackExchange" 

and then all "New category-theory questions" messages will get grouped
together in the Summary window?  So, I defined:

(setq vm-subject-ignored-suffix
      (concat " for 
\\(Jan\\|Feb\\|Mar\\|Apr\\|May\\|Jun\\|Jul\\|Aug\\|Sep\\|Oct\\|Nov\\|Dec\\)"
              " [0-9]* - Stack Exchange\\|"
              vm-subject-ignored-suffix))

and reloaded the folder.  Bingo, I now have a few hundred lines in the
Summary window rather than thousands, and I get to see the other important
email that was getting swamped out by these alerts.

-----

This second trick might be useful if you get a lot of email via mailing
lists or bug trackers that add "subject tags".  For example, the subject
line for a new bug report on the Launchpad looks something like this:

   [Bug 1072069] [NEW] summary crashes for international characters (8.1.0)

The stuff in brackets "[Bug 1072069]" and "[NEW]" were added by the
Launchpad mailer.  They were not part of the original subject of the bug
report.  In our parlance, these are "subject tags".

Given that I allocate something like 25 characters for the subject in my
Summary window, these subject tags were crowding out the real subject.  This
problem annoyed me enough that I ended up adding a feature to VM.  There is
now a new variable

   vm-subject-tag-prefix

using which you can describe the format of the subject tags, and a way to
turn on or off the inclusion of subject tags in the Summary window using a
variable `vm-summary-strip-subject-tags'.  My `vm-subject-tag-prefix' is as
follows:

(setq vm-subject-tag-prefix 
      (concat
       "\\[[^]:]*][: \n\t]*"            ; mailing-list tags
       "\\|bug#[0-9]*:[ \n\t]*"         ; emacs debbugs
       ))

This removes all square-bracketed subject tags and also message from the
Emacs debbugs tracker which uses a different convention for adding its
subject tag.

That was good.  But I still wanted the subject tags retained in the INBOX
folders, because the mail comes from a variety of sources and I want to be
able to quickly eyeball it for important stuff.  However, once I have filed
away the mail in archival folders, I wanted the subject tags to disappear.
The solution was to make a buffer-local version of the variable
`vm-summary-strip-subject-tags' and turn it on/off based on the name of the
folder.  So, I added vm-visit-folder-hook as follows:

(defun retain-subject-tags-for-inbox ()
  "Setq `vm-summay-strip-subject-tags' to nil for all IMAP folders
named \"inbox\"." 
  (when (and vm-folder-access-data (vm-folder-imap-maildrop-spec))
    (cond ((equal 
            (downcase
             (vm-imap-folder-for-spec (vm-folder-imap-maildrop-spec)))
            "inbox")
           (set (make-local-variable 'vm-summary-strip-subject-tags) nil)))))

(add-hook 'vm-visit-folder-hook 'retain-subject-tags-for-inbox)

I think the problem is solved now.

Cheers,
Uday