Merge branch 'mg/placeholders-are-lowercase'

* mg/placeholders-are-lowercase:
  Make <identifier> lowercase in Documentation
  Make <identifier> lowercase as per CodingGuidelines
  Make <identifier> lowercase as per CodingGuidelines
  Make <identifier> lowercase as per CodingGuidelines
  CodingGuidelines: downcase placeholders in usage messages

diff --cc builtin/config.c
Simple merge

diff --cc builtin/fast-export.c
Simple merge

diff --cc builtin/merge.c
Simple merge