tests/test-fuzz-targets.t

narrow: don't send the changelog information when widening without ellipses

When we widen anon-ellipses narrow copy, the server sends the changelog
information of all the changesets. The code was copied from ellipses case and in
ellipses cases, it's required to send the new changelog data.

But in non-ellipses cases, we don't need to send the changelog data as we will
have all the changesets locally.

Before this patch, there was a overhead of ~8-10 mins on each widening call
because of all the changelog information being pulled and being applied. After
this patch, we no more pull the changelog information. So this patch can save ~5
mins on Mozilla repo on each widening and more on repos which have more
changesets.

When we apply an empty changelog from changegroup, there is a devel-warn. This
patch kind of hacks to silence that devel-warn.

Differential Revision: https://phab.mercurial-scm.org/D4639

#require test-repo

  $ cd $TESTDIR/../contrib/fuzz

#if clang-libfuzzer
  $ make -s clean all
#endif
#if no-clang-libfuzzer clang-6.0
  $ make -s clean all CC=clang-6.0 CXX=clang++-6.0
#endif
#if no-clang-libfuzzer no-clang-6.0
  $ exit 80
#endif

Just run the fuzzers for five seconds each to verify it works at all.
  $ ./bdiff -max_total_time 5
  $ ./mpatch -max_total_time 5
  $ ./xdiff -max_total_time 5