Merge branch 'jc/tag-doc'

Our documentation used to assume having files in .git/refs/*
directories was the only to have branches and tags, but that is not
true for quite some time.

* jc/tag-doc:
  Documentation: do not mention .git/refs/* directories

diff --cc Documentation/git-filter-branch.txt
Simple merge

diff --cc Documentation/git-fsck.txt
Simple merge

diff --cc Documentation/git-pack-refs.txt
Simple merge

diff --cc Documentation/git-tag.txt
Simple merge