rust-dirstatemap: add unit tests
These were missing and have already proven valuable since they have found
two bugs (fixed in previous patches).
There may be other behavior to test, but this gives us a decent coverage.
Differential Revision: https://phab.mercurial-scm.org/D12524
How to add fuzzers (partially cribbed from oss-fuzz[0]):
1) git clone https://github.com/google/oss-fuzz
2) cd oss-fuzz
3) python infra/helper.py build_image mercurial
4) docker run --cap-add=SYS_PTRACE -it -v $HG_REPO_PATH:/hg-new \
gcr.io/oss-fuzz/mercurial bash
5) cd /src
6) rm -r mercurial
7) ln -s /hg-new mercurial
8) cd mercurial
9) compile
10) ls $OUT
Step 9 is literally running the command "compile", which is part of
the docker container. Once you have that working, you can build the
fuzzers like this (in the oss-fuzz repo):
python infra/helper.py build_fuzzers --sanitizer address mercurial $HG_REPO_PATH
(you can also say "memory", "undefined" or "coverage" for
sanitizer). Then run the built fuzzers like this:
python infra/helper.py run_fuzzer mercurial -- $FUZZER
0: https://github.com/google/oss-fuzz/blob/master/docs/new_project_guide.md