tests/test-fuzz-targets.t

commit: use `dirstate.change_files` to scope the associated `addremove`

This was significantly more complicated than I expected, because multiple
extensions get in the way.

I introduced a context that lazily open the transaction and associated context
to work around these complication. See the inline documentation for details.

Introducing the wrapping transaction remove the need for dirstate-guard (one of
the ultimate goal of all this), and slightly affect the result of a `hg
rollback` after a `hg commit --addremove`. That last part is deemed fine. It
aligns the behavior with what happens after a failed `hg commit --addremove` and
nobody should be using `hg rollback` anyway.

The small output change in the test come from the different transaction timing
and fact the transaction now backup the dirstate before the addremove, which
might mean "no file to backup" when the repository starts from an empty state.

#require test-repo py3

  $ cd $TESTDIR/../contrib/fuzz
  $ OUT=$TESTTMP ; export OUT

which(1) could exit nonzero, but that's fine because we'll still end
up without a valid executable, so we don't need to check $? here.

  $ if which gmake >/dev/null 2>&1; then
  >     MAKE=gmake
  > else
  >     MAKE=make
  > fi

  $ havefuzz() {
  >     cat > $TESTTMP/dummy.cc <<EOF
  > #include <stdlib.h>
  > #include <stdint.h>
  > int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) { return 0; }
  > int main(int argc, char **argv) {
  >     const char data[] = "asdf";
  >     return LLVMFuzzerTestOneInput((const uint8_t *)data, 4);
  > }
  > EOF
  >     $CXX $TESTTMP/dummy.cc -o $TESTTMP/dummy \
  >        -fsanitize=fuzzer-no-link,address || return 1
  > }

Try to find a python3-config that's next to our sys.executable. If
that doesn't work, fall back to looking for a global python3-config
and hope that works out for the best.
  $ PYBIN=`"$PYTHON" -c 'import sys, os; print(os.path.dirname(sys.executable))'`
  $ if [ -x "$PYBIN/python3-config" ] ; then
  >   PYTHON_CONFIG="$PYBIN/python3-config"
  > else
  >   PYTHON_CONFIG="`which python3-config`"
  > fi

#if clang-libfuzzer
  $ CXX=clang++ havefuzz || exit 80
  $ $MAKE -s clean all PYTHON_CONFIG="$PYTHON_CONFIG"
#endif
#if no-clang-libfuzzer clang-6.0
  $ CXX=clang++-6.0 havefuzz || exit 80
  $ $MAKE -s clean all CC=clang-6.0 CXX=clang++-6.0 PYTHON_CONFIG="$PYTHON_CONFIG"
#endif
#if no-clang-libfuzzer no-clang-6.0
  $ exit 80
#endif

  $ cd $TESTTMP

Run each fuzzer using dummy.cc as a fake input, to make sure it runs
at all. In the future we should instead unpack the corpus for each
fuzzer and use that instead.

  $ for fuzzer in `ls *_fuzzer | sort` ; do
  >   echo run $fuzzer...
  >   ./$fuzzer dummy.cc > /dev/null 2>&1 
  > done
  run bdiff_fuzzer...
  run dirs_fuzzer...
  run dirstate_fuzzer...
  run fm1readmarkers_fuzzer...
  run fncache_fuzzer...
  run jsonescapeu8fast_fuzzer...
  run manifest_fuzzer...
  run mpatch_fuzzer...
  run revlog_fuzzer...
  run xdiff_fuzzer...

Clean up.
  $ cd $TESTDIR/../contrib/fuzz
  $ $MAKE -s clean