view mercurial/__init__.py @ 4979:06abdaf78788

revlog: add a magic null revision to our index

We expand our index by one entry so that index[nullrev] points to a
unique entry, the null revision. This naturally eliminates numerous
extra tests in the performance-sensitive index access functions, most
of which are now trivial again.

Adding new entries is now done with insert(-1, e) rather than
append(e).