copies-rust: add a macro-based unit-testing framework `compare_values`, `merge_copies_dict`, and `CombineChangesetCopies` are APIs whose signatures involve non-trivial types. Calling them directly in unit tests would involve a lot of verbose setup code that obscures the meaningful parts of a given test case. This adds a macro-based test-harness with pseudo-syntax to tersely create arguments and expected return values in the correct types. For now there is only one (not particularly meaningful) test case per tested function, just to exercize the macros. Differential Revision: https://phab.mercurial-scm.org/D10071

copies-rust: rewrite ChangedFiles binary parsing by using the new from-bytes-safe crate and a custom struct that encodes the expected data structure. Differential Revision: https://phab.mercurial-scm.org/D10068

tags: validate nodes in _getfnodes() and update cache in case of unknown nodes `hgtagsfnodescache` can contain unknown nodes due to cache corruption and this lead to a traceback on operations like `hg tags` as we don't validate nodes. This patch validates that all filenodes returned after `hgtagsfnodescache` are known to the repository. If there exists any unknown filenode, we force recompute it and update the cache. The test change demonstrates the fix. Differential Revision: https://phab.mercurial-scm.org/D10083

debugtagscache: verify that filenode is correct Previous patch from Matt demonstrates that `debugtagscache` does not warn about filenode being unknown which can be caused by a corrupted cache. We start by showing that it's an unknown node. Differential Revision: https://phab.mercurial-scm.org/D10015

tests: demonstrate a case where a corrupt tag cache causes an abort I happened to hit this trying to cover other cases around valid vs missing entries. I have no idea if this is something that could occur more naturally (similar to how a missing file node in `hgtagsfnodes1` can occur after a strip). There is a test just above this added in f5a7cf0adb12 mentioning it "overwrites the junk", though that tests truncation instead of actual garbage. But since this is just a cache, it probably shouldn't abort with a cryptic message like this. The two options I see both have downsides- either rebuild the cache (and potentially take a long time), or hint to the user to run a debug command. Differential Revision: https://phab.mercurial-scm.org/D9812

debugcommands: prevent using `is False` I was touching this code in a future patch and marmoute warned about usage of `is False` here. Quoting marmoute: ``` "is False" is going to check if the object you have the very same object in memory than the one Python allocated for False (in practice 0) This will "mostly work" on cpython because of implementation details, but is semantically wrong and can start breaking unexpectedly ``` Differential Revision: https://phab.mercurial-scm.org/D10014

hgtagsfnodes: refactor code to compute fnode into separate fn I plan to use this code at one more place while fixing a bug caused by an invalid fnode present in cache. Differential Revision: https://phab.mercurial-scm.org/D10013