Merge branch 'nd/complete-config-vars'

"git help --config" (which is used in command line completion)
missed the configuration variables not described in the main
config.txt file but are described in another file that is included
by it, which has been corrected.

* nd/complete-config-vars:
  generate-cmdlist.sh: collect config from all config.txt files

diff --cc Documentation/config.txt
Simple merge