Merge branch 'sg/complete-configuration-variables'

Merge branch 'sg/complete-configuration-variables'

Command line completion updates for "git -c var.name=val"

* sg/complete-configuration-variables:
  completion: complete config variables and values for 'git clone --config='
  completion: complete config variables names and values for 'git clone -c'
  completion: complete values of configuration variables after 'git -c var='
  completion: complete configuration sections and variable names for 'git -c'
  completion: split _git_config()
  completion: simplify inner 'case' pattern in __gitcomp()
  completion: use 'sort -u' to deduplicate config variable names
  completion: deduplicate configuration sections
  completion: add tests for 'git config' completion
  completion: complete more values of more 'color.*' configuration variables
  completion: fix a typo in a comment