Merge branch 'maint-1.6.4' into maint-1.6.5

Merge branch 'maint-1.6.4' into maint-1.6.5

* maint-1.6.4:
  Fix mis-backport of t7002
  base85: Make the code more obvious instead of explaining the non-obvious
  base85: encode_85() does not use the decode table
  base85 debug code: Fix length byte calculation
  checkout -m: do not try to fall back to --merge from an unborn branch
  branch: die explicitly why when calling "git branch [-a|-r] branchname".
  textconv: stop leaking file descriptors
  commit: --cleanup is a message option
  git count-objects: handle packs bigger than 4G
  t7102: make the test fail if one of its check fails