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).
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<title>Mercurial Error</title>
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<h2>Mercurial Error</h2>
<p>
An error occured while processing your request:
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#error|escape#
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