sparse: add timing block for parsing sparse configs
This was showing up in an operation I was doing today, and I'd like to
be able to get trace spans for it instead of just profiler samples.
Differential Revision: https://phab.mercurial-scm.org/D12186
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
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Basic install::
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing::
$ make local # build for inplace usage
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See https://mercurial-scm.org/ for detailed installation
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Notes for packagers
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Mercurial ships a copy of the python-zstandard sources. This is used to
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