annotate: start pager soon after command options are validated It helps extracting helper class.

annotate: check and update command options first It helps extracting helper class.

annotate: format local tables in less-dense form I'll move these to a class, where one-extra indent will be needed.

perf: rename version flag of perfchangegroupchangelog to cgversion The version flag conflicts with the global version flag and does not work. Differential Revision: https://phab.mercurial-scm.org/D5297 Differential Revision: https://phab.mercurial-scm.org/D5298

procutil: don't allow the main 'hg' script to be treated as the Windows exe Previously, there were a handful of errors like this: $ hg prefetch --repack (running background incremental repack) + abort: %1 is not a valid Win32 application + [255] CreateProcess() doesn't append .exe when `lpApplicationName` contains a path, and a python script isn't directly executable.

remotefilelog: drop some compatibility cruft for finding the hg exeutable

branchmap: build the revbranchcache._namesreverse() only when required On big repositories with a lot of named branches and that also increasing over time, building of this dict can be expensive and shows up in profile. For our internal repository, this saves ~0.05 seconds. Thanks to Yuya for suggesting using util.propertycache() and util.clearcachedproperty(). Differential Revision: https://phab.mercurial-scm.org/D5291

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.

cext: increment the `parsers` module version We introduced a new `slicechunktodensity` method to the index.

sparse-revlog: introduce native (C) implementation of slicechunktodensity This is a C implementation of `_slicechunktodensity` in the `mercurial/revlogutils/deltas.py` file. The algorithm involves a lot of integer manipulation and low-level access to index data. Having a C implementation of it raises a large performance improvement. See later changeset in this series for details.