The generation of cache files like tags.cache and branchheads.cache is not an
actual reflection of things changing in the whole of the .hg directory (like eg
a commit or a rebase or something) but instead these cache files are just part
of bookkeeping. As such its convienant to allow various clients to ignore file
events to do with these cache files which would otherwise cause a double
refresh. Eg one refresh might occur after a commit, but the act of refreshing
after the commit would cause Mercurial to generate a new branchheads.cache which
would then cause a second refresh, for clients.
However if these cache files are moved into a directory like eg .hg/cache/ then
GUI clients on OSX (and possibly other platforms) can happily ignore file events
in this cache directory.
This patch adds a case to test-hardlinks.t which demonstrates that
hardlinks in the working directory are broken up (using 'hg update').
Motivation for this patch:
'hg help clone' shows copying repositories *and* the working directory
using 'cp -al', creating hardlinks in the *working directory* too (not
just in the store).
Note that we can't use 'cp -al' since for example MacOS X doesn't
support these options on cp. I'm thus using the same trick as in
test-hardlinks-safety.t for creating hardlinks in the working dir.
