tests/test-gendoc-sv.t

nodemap: add a test about racy commit during stream clone

That test show that the resulting client nodemap is different from the server
one. This happens because the server one transferred a corrupted node map. The
data file match the pre-commit content while the docket has post commit content.
As the result the nodemap was detected invalid and recomputed.

When running without the rust implementation, the code is also generating a new
datafile unconditionally, This mean the older file is no longer there are
transfer time, resulting in a crash.

We will fix this issue later, but we start with writing tests highlighting the
issue.

Differential Revision: https://phab.mercurial-scm.org/D10479

#require docutils gettext

  $ $TESTDIR/check-gendoc sv
  checking for parse errors