match: strengthen visit_children_set invariant, Recursive means "all files" My previous interpretation of "Recursive" was too relaxed: I thought it instructed the caller to do something like this: > you can stop calling `visit_children_set` because you'll need to descend into > every directory recursively, but you should still check every file if it > matches or not Whereas the real instruction seems to be: > I guarantee that everything in this subtree matches, you can stop > querying the matcher for all files and dirs altogether. The evidence to support this: - the test actually passes with the stronger invariant, revealing no exceptions from this rule - the implementation of `visit_children_set` for `DifferenceMatcher` clearly relies on this requirement, so it must hold for that not to lead to bugs.

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#require emacs

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  $ emacs -q -no-site-file -batch -l $TESTDIR/../contrib/hg-test-mode.el \

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  >  -f ert-run-tests-batch-and-exit

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  Running 1 tests (*) (glob)

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     passed  1/1  hg-test-mode--compilation-mode-support* (glob)

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  Ran 1 tests, 1 results as expected* (glob)

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