Date: Wed, 21 Dec 2011 09:40:08 -0500
From: Austin Clements <amdragon@MIT.EDU>
To: David Edmondson <dme@dme.org>
Subject: Re: [PATCH] emacs: create patch filename from subject for inline
	patch fake parts
Message-ID: <20111221144008.GG10376@mit.edu>
References: <1321657368-13872-1-git-send-email-jani@nikula.org>
	<87aa6nxb3o.fsf@nikula.org> <20111220215229.GF10376@mit.edu>
	<cun4nwuxota.fsf@hotblack-desiato.hh.sledj.net>
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I would definitely go with the latter.

It might feel less unwieldy with a shorter variable name than
"filename", since that has to be repeated so many times.  (It's also
not really a filename in the middle of the replace process.)

This is splitting hairs, but in my original suggestion, I was thinking
something like

  (let* ((s subject)
         (s (replace-regexp-in-string "^ *\\(\\[[^]]*\\]\\)? *" "" s))
         (s (replace-regexp-in-string "[. ]*$" "" s))
         (s (replace-regexp-in-string "[^A-Za-z0-9._-]+" "-" s))
         (s (replace-regexp-in-string "\\.+" "." s))
         (s (substring s 0 (min (length s) 50))))
     (concat s ".patch"))

Out of curiosity, where'd the regexps come from?  They all seem
reasonable, but some of them seem somewhat arbitrary.

Quoth David Edmondson on Dec 21 at  9:21 am:
> On Tue, 20 Dec 2011 16:52:52 -0500, Austin Clements <amdragon@MIT.EDU> wrote:
> > Seems like a definite improvement, but perhaps a let* instead of all
> > of the setq's?
> 
> What would be a lispy approach? I tried:
> 
> (defun notmuch-subject-to-patch-filename (subject)
>   "Convert a typical patch mail subject line into a suitable filename."
>   (concat 
>    (let ((filename subject)
> 	 (transforms
> 	  '(("^ *\\(\\[[^]]*\\]\\)? *" . "")
> 	    ("[. ]*$" . "")
> 	    ("[^A-Za-z0-9._-]+" . "-")
> 	    ("\\.+" . "."))))
>      (mapc (lambda (transform)
> 	     (setq filename (replace-regexp-in-string (car transform) (cdr transform) filename)))
> 	   transforms)
>      (substring filename 0 (min (length filename) 50)))
>    ".patch"))
> 
> ...but that seems a bit unwieldy. `let*' looks best, but still feels a
> bit odd:
> 
> (defun notmuch-subject-to-patch-filename (subject)
>   "Convert a typical patch mail subject line into a suitable filename."
>   (concat 
>    (let* ((filename (replace-regexp-in-string "^ *\\(\\[[^]]*\\]\\)? *" "" subject))
> 	  (filename (replace-regexp-in-string "[. ]*$" "" filename))
> 	  (filename (replace-regexp-in-string "[^A-Za-z0-9._-]+" "-" filename))
> 	  (filename (replace-regexp-in-string "\\.+" "." filename)))
>      (substring filename 0 (min (length filename) 50)))
>    ".patch"))
> 
> dme.