rust-dirstate: create dirstate submodule
This change is here to facilitate a future patch that is written in a
different file. I expect this module to grow a few different files.
Differential Revision: https://phab.mercurial-scm.org/D6389
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"show_commit_url": "https://www.mercurial-scm.org/repo/hg/rev/",
"benchmark_dir": "benchmarks",
"env_dir": "../.asv/env",
"results_dir": "../.asv/results",
"html_dir": "../.asv/html"
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