To get the ball rolling more quickly, the download_refs fuzzer for
libgit2 was first implemented directly in oss-fuzz. But as we want to
ensure that we're not breaking fuzzers and thus at least build them as
part of our CI, the goal has been to upstream them into libgit2.
This commit removes the download_refs fuzzer and its corpus in favor of
using the upstreamed fuzzer. Furthermore, the build script is
generalized to automatically pick up new fuzzers named according to a
certain pattern, as we already added a second packfile fuzzer.
* Add a libgit2 fuzzer for the `git fetch` client
* Use a fresh remote each time
* Build fewer things, use fewer deps
* no ssh, either
* Add a corpus with one file.
Slightly tweaked network dump of a `git clone` on a tiny repo.
* auto_ccs is a list
* Rename the fuzzer
* only email in project.yaml
* Use `master`
I had left in a `-b oss-fuzz` from testing off my fork
devtty1er