fuzz: new fuzzer for cext/manifest.c This is a bit messy, because lazymanifest is tightly coupled to the cpython API for performance reasons. As a result, we have to build a whole Python without pymalloc (so ASAN can help us out) and link against that. Then we have to use an embedded Python interpreter. We could manually drive the lazymanifest in C from that point, but experimentally just using PyEval_EvalCode isn't really any slower so we may as well do that and write the innermost guts of the fuzzer in Python. Leak detection is currently disabled for this fuzzer because there are a few global-lifetime things in our extensions that we more or less intentionally leak and I didn't want to take the detour to work around that for now. This should not be pushed to our repo until https://github.com/google/oss-fuzz/pull/1853 is merged, as this depends on having the Python tarball around. Differential Revision: https://phab.mercurial-scm.org/D4879

revlog: rename _cache to _revisioncache "cache" is generic and revlog instances have multiple caches. Let's be descriptive about what this is a cache for. Differential Revision: https://phab.mercurial-scm.org/D4866

testing: add file storage integration for bad hashes and censoring In order to implement these tests, we need a backdoor to write data into storage backends while bypassing normal checks. We invent a callable to do that. As part of writing the tests, I found a bug with censorrevision() pretty quickly! After calling censorrevision(), attempting to access revision data for an affected node raises a cryptic error related to malformed compression. This appears to be due to the revlog not adjusting delta chains as part of censoring. I also found a bug with regards to hash verification and revision fulltext caching. Essentially, we cache the fulltext before hash verification. If we look up the fulltext after a failed hash verification, we don't get a hash verification exception. Furthermore, the behavior of revision(raw=True) can be inconsistent depending on the order of operations. I'll be fixing both these bugs in subsequent commits. Differential Revision: https://phab.mercurial-scm.org/D4865

testing: add file storage tests for getstrippoint() and strip() Differential Revision: https://phab.mercurial-scm.org/D4864

wireprotov2: always advertise raw repo requirements I'm pretty sure my original thinking behind making it conditional on stream clone support was that the behavior mirrored wire protocol version 1. I don't see a compelling reason for us to not advertise the server's storage requirements. The proper way to advertise stream clone support in wireprotov2 would be to not advertise the command(s) required to perform stream clone or to advertise a separate capability denoting stream clone support. Stream clone isn't yet implemented on wireprotov2, so we can cross this bridge later. Differential Revision: https://phab.mercurial-scm.org/D4863

tests: don't be as verbose in wireprotov2 tests I don't think that printing low-level I/O and frames is beneficial to testing command-level functionality. Protocol-level testing, yes. But command-level functionality shouldn't care about low-level details in most cases. This output makes tests more verbose and harder to read. It also makes them harder to maintain, as you need to glob over various dynamic width fields. Let's remove these low-level details from many of the wireprotov2 tests. Differential Revision: https://phab.mercurial-scm.org/D4861

repository: define and use revision flag constants Revlogs have a per-revision 2 byte field holding integer flags that define how revision data should be interpreted. For historical reasons, these integer values are sent verbatim on the wire protocol as part of changegroup data. From a semantic standpoint, the flags that go out over the wire are different from the flags stored internally by revlogs. Failure to establish this semantic distinction creates unwanted strong coupling between revlog's internals and the wire protocol. This commit establishes new constants on the repository module that define the revision flags used by the wire protocol (and by some internal storage APIs, sadly). The changegroups internals documentation has been updated to document them explicitly. Various references throughout the repo now use the repository constants instead of the revlog constants. This is done to make it clear that we're operating on generic revision data and this isn't tied to revlogs. Differential Revision: https://phab.mercurial-scm.org/D4860

context: reverse conditional branch order in introrev Positive logic will be simpler to follow. It will help to clarify coming refactoring.

context: drop a redundant fast path in introrev Now that _adjustlinkrev fast path this case itself, we no longer need an extra conditional. A nice side effect is that we are no longer calling `self.rev()`. In case where `_descendantrev` is set, calling `self.rev` will trigger a potentially expensive `_adjustlinkrev` call. So blindly calling `self.rev()` to avoid another `_adjustlinkrev` call can be counterproductive. Note that `_descendantrev` is currently never taken into account in `introrev` so far which is wrong. We'll fix that in changeset later in this series.

context: fast path linkrev adjustement in trivial case If the search starts from the linkrev, there is nothing to adjust.