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).

adding a
Now at: a.patch
applying b.patch
applying c.patch
Now at: c.patch
Now at: b.patch