sparse-revlog: put the native implementation of slicechunktodensity to use
When possible, the C implementation of delta chain slicing will be used.
providing a large boost in performance for this operation.
To take a practical example of restoring manifest revision '
59547c40bc4c' for
a reference NetBeans repository (using sparse-revlog). The media time of the
step `slice-sparse-chain` of `perfrevlogrevision` improve from 0.660 ms to
0.098 ms;
The full series move delta chain slicing from 1.120 ms to 0.098 ms;
Implementing _slicechunktosize into C would yield further improvements.
However, the performance seems good enough for now.
.. Common link and substitution definitions.
.. |hg(1)| replace:: **hg**\ (1)
.. _hg(1): hg.1.html
.. |hgrc(5)| replace:: **hgrc**\ (5)
.. _hgrc(5): hgrc.5.html
.. |hgignore(5)| replace:: **hgignore**\ (5)
.. _hgignore(5): hgignore.5.html