add other dir/file case to test for
issue322.
load extensions from every hgrc.
before this change only extensions in global hgrc files were loaded.
now extensions in per-repo hgrc are loaded.
Fix bug #345.
The last hit for a file might have been before the last window, so we
can't clear copies. To reduce the load, we only store real copy
entries instead of storing hashes for every revision.