Merge 'build-in git-mktree'

* commit '633e3556ccbc': (5835 commits)
  build-in git-mktree
  allow -t abbreviation for --track in git branch
  gitweb: Remove function prototypes (cleanup)
  Documentation: cloning to empty directory is allowed
  Clarify kind of conflict in merge-one-file helper
  git config: clarify --add and --get-color
  archive-tar.c: squelch a type mismatch warning
  Start 1.6.4 development
  Start 1.6.3.1 maintenance series.
  GIT 1.6.3
  t4029: use sh instead of bash
  t4200: convert sed expression which operates on non-text file to perl
  t4200: remove two unnecessary lines
  t/annotate-tests.sh: avoid passing a non-newline terminated file to sed
  t4118: avoid sed invocation on file without terminating newline
  t4118: add missing '&&'
  t8005: use egrep when extended regular expressions are required
  git-clean doc: the command only affects paths under $(cwd)
  improve error message in config.c
  t4018-diff-funcname: add cpp xfuncname pattern to syntax test
  ...