Re: DEP14 policy for two dots

[Ian Jackson <ijackson@chiark.greenend.org.uk>]

Ian Jackson writes ("Re: DEP14 policy for two dots"):
> Raphael Hertzog writes ("Re: DEP14 policy for two dots"):
> > On Fri, 04 Nov 2016, Ian Jackson wrote:
> > > My proposal is reversible.  It does not need to be extensible.
> > 
> > So what about "..."? Would it give ".#.#."?
> 
> Yes.  I said (fixing my bug):
> 
>  > Insert "#":
>  >    - between each pair of adjacent dots
>  >    - after any trailing dot
>  >    - before any leading dot
>       - after the `.' of a trailing `.lock'
> 
> The latter is necessary because git reserves .lock.  (!)
> The summary is `add # after any troublesome dot' (discounting leading
> dots which you say are now illegal in Debian).
> 
> I'm running some exhaustive tests to check that this rule is
> sufficient, because I'm not sure I trust the git docs.

I have now:

 * Read the code in git upstream master.  It's not particularly easy
   to analyse conclusively, but I'm pretty sure it doesn't have any
   special cases which involve longer strings than ".lock".  I felt I
   was able to identify the manpage rule corresponding to each element
   of the logic.

 * Conducted an exhaustive search of all strings of length 6
   or less.  Specifically, I generated all strings of between
   zero and 6 characters from this set (in C notation):

 	   "0123456789"
	   "abcdefghijklmnopqrstuvwxyz"
	   "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	   ".-+:~"

   filtered them by whether the `parseversion' function in
   dpkg likes them, escaped them with the following perl
   script

	 #!/usr/bin/perl -pw
	 use strict;

	 y/:~/%_/;
	 s/\.(?=\.|$|lock$)/.#/g;

   prepended "refs/tags/" to each one and fed them to
   git-check-ref-format (modified to run in a pipe mode).

   I also verified that when I don't escape ".lock", my exhaustive
   search correctly detects the illegal ref name "refs/tags/1.lock"
   genrated by version "1.lock" (and similar).

> The reverse rule is to convert _ and % and delete all #.

Quoted for completeness.

Ian.

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