contrib/hgsh: Check for .hg/store as well as .hg/data. This is required by the new repository layout.

MQ: tidy up if a qpush is interrupted. This aborts the transaction, makes sure the dirtied dirstate isn't written out, and cleans up the working directory.

Merge with stable

merge: fix spurious merges for copies in linear updates We make better use of contexts to accurately identify copies that don't need merges. Add a simple test and update other tests.