tests/test-gendoc-el.t

sparse-revlog: add a `trim_endidx` function in C

We are about to implement a native version of `slicechunktodensity`. For
clarity, we introduce the helper functions first.

This function implement a subpart of the python function `_trimchunk` in
`mercurial/revlogutils/deltas.py`. Handling of actual Python objects is left
to the caller function.

#require docutils gettext

  $ $TESTDIR/check-gendoc el
  checking for parse errors