m4_version_compare and new version numbering [was: distcheck fails with autotest...]

[Eric Blake]

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According to Jim Meyering on 11/2/2007 1:01 PM:
>> Also, why is the current version something like 2.61a-248-dc51?
>> That compares wrongly in order with 2.61b which is what post 2.61a
>> CVS versions had.
> 
> Because these versions are post-2.61a, and pre-2.61b :-)

Hmm.  Maybe it's time to rewrite m4_version_compare to treat `-' the same
as `.' when it occurs in the original version strings.  Currently,
m4_version_unletter (a key component in AC_PREREQ) interprets the - in the
string as a subtraction, with the following results:

m4_version_unletter([2.61b])
=> 2.62.-1.11
m4_version_unletter([2.61a-248-dc51])
=> 2.62.-1.-239.-1.622261

Side-by-side, this correctly compares 61a-nnn as smaller than 61b.
However, for increasing nnn, the further you get from 61a, the more
negative the result gets, which is the wrong direction.

I'll throw together a patch when I have more time.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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