test-dirstate: fix detection of Rust environment variable
The Rust path never actually worked. This change also improves clarity of the
comment. The next change will ensure we print something when this check fails.
Differential Revision: https://phab.mercurial-scm.org/D12601
# See http://EditorConfig.org for the specification
root = true
[*.py]
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indent_style = space
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end_of_line = lf
[*.{c,h}]
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indent_style = tab
trim_trailing_whitespace = true
end_of_line = lf
[*.t]
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indent_style = space
trim_trailing_whitespace = false
end_of_line = lf