Summary:
This diff replaces eden's dependencies on failure::Error with anyhow::Error.
Failure's error type requires all errors to have an implementation of failure's own failure::Fail trait in order for cause chains and backtraces to work. The necessary methods for this functionality have made their way into the standard library error trait, so modern error libraries build directly on std::error::Error rather than something like failure::Fail. Once we are no longer tied to failure 0.1's Fail trait, different parts of the codebase will be free to use any std::error::Error-based libraries they like while still working nicely together.
Reviewed By: xavierd
Differential Revision: D18576093
fbshipit-source-id: e2d862b659450f2969520d9b74877913fabb2e5d
Any native code (C/C++/Rust) that Mercurial (either core or extensions)
depends on should go here. Python code, or native code that depends on
Python code (e.g. #include <Python.h> or use cpython) is disallowed.
As we start to convert more of Mercurial into Rust, and write new paths
entrirely in native code, we'll want to limit our dependency on Python, which is
why this barrier exists.
See also hgext/extlib/README.md, mercurial/cext/README.mb.
How do I choose between lib and extlib (and cext)?
If your code is native and doesn't depend on Python (awesome!), it goes here.
Otherwise, put it in hgext/extlib (if it's only used by extensions) or
mercurial/cext (if it's used by extensions or core).
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