commands: move checkformat to bookmarks module
commands.bookmark has grown quite large with two closures already. Let's
split this up (and in the process allow extensions to override the
default behavior).
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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