tests/test-parseindex2.py.out

util: make sortdict.keys() return a copy

dict.keys() is documented to return a copy, so it's surprising that
sortdict.keys() did not. I noticed this because we have an extension
that calls readlocaltags(). That method tries to remove any tags that
point to non-existent revisions (most likely stripped). However, since
it's unintentionally working on the instance it's modifying, it
sometimes fails to remove tags when there are multiple bad tags in a
row. This was not caught because localrepo.tags() does an additional
layer of filtering.

sortdict is also used in other places, but I have not checked whether
its keys() and/or __delitem__() methods are used there.

done