Merge branch 'jn/preformatted-doc-url'

The top level documentation "git help git" still pointed at the
documentation set hosted at now-defunct google-code repository.
Update it to point to https://git.github.io/htmldocs/git.html
instead.

* jn/preformatted-doc-url:
  doc: git-htmldocs.googlecode.com is no more

diff --cc Documentation/git.txt
Simple merge