extdiff: copy back files to the working directory if the size changed In theory, it should be enough to pay attention only to the modification time when detecting if a snapshotted working directory file changed. In practice, BeyondCompare preserves all file attributes when syncing files at the directory level. (If you open the file and sync individual hunks, then mtime does change, and everything was being copied back as desired.) I'm not sure how many other synchronization tools would trigger this issue, but it's annoyingly inconsistent (if a single file is diffed, it isn't snapshotted, so the same BeyondCompare file sync operation _is_ visible, because wdir() is updated in place. I filed a bug with them, and they stated it is on their wish list, but won't be fixed in the near term. This isn't a complete fix (there is still the case of the size not changing), but this seems like a trivial enough change to fix most of the problem. I suppose we could fool around with making files in the other snapshot readonly, and copy back if we see the readonly bit copied. That seems pretty hacky though, and only works if the external tool copies all attributes.

test-extdiff: enable a previously failing test on Windows

test-extdiff: narrow the range of an '#if execbit' block Now that output can be conditionalized, the few `chmod +x` specific outputs can be conditionalized, and the rest of the tests run as normal. Disable one test that is failing on Windows for now.

test-extdiff: deduplicate tests

test-extdiff: fill in a missing Windows test

policy: eliminate ".pure." from module name only if marked as dual So we can switch cext/pure modules to new layout one by one.