windows: avoid deleting non-empty reparse points
If a hg repository including working directory is a reparse point (directory
symlinked or a junction point), then using os.removedirs will remove the
reparse point erroneously. This is fixed by only removing directories if they
are empty.
#header#
<title>#repo|escape#: #file|escape# history</title>
<description>#file|escape# revision history</description>
#entries%filelogentry#
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