Merge branch 'nd/conditional-config-include'

The configuration file learned a new "includeIf.<condition>.path"
that includes the contents of the given path only when the
condition holds.  This allows you to say "include this work-related
bit only in the repositories under my ~/work/ directory".

* nd/conditional-config-include:
config: add conditional include
config.txt: reflow the second include.path paragraph
config.txt: clarify multiple key values in include.path

diff --cc Documentation/config.txt
Simple merge

diff --cc config.c
Simple merge