sed --posix

[Simon Josefsson]

I'm tracking down why gnulib-tool no longer updates license headers
correctly for me, and it boils down to me upgrading sed recently, and
that gnulib-tool invokes sed with --posix.  This works:

address@hidden:~/src/libidn master$ echo 'version 2  '|sed -e 's/version 
\(2\|2\.1\)\([ ,]\)/version 3\2/g'
version 3  

But adding --posix makes it fail:

address@hidden:~/src/libidn master$ echo 'version 2  '|sed --posix -e 
's/version \(2\|2\.1\)\([ ,]\)/version 3\2/g'
version 2  

I'm using GNU sed v4.2 from debian testing.  I suspected the final g
parameter to s/// but removing that didn't help.

Is this a sed bug?  It kind of seems like it, but I'm not certain.

Thanks,
/Simon