Merge git://git.bogomips.org/git-svn

* git://git.bogomips.org/git-svn:
  git-svn: Warn about changing default for --prefix in Git v2.0
  Documentation/git-svn: Promote the use of --prefix in docs + examples
  git-svn.txt: elaborate on rev_map files
  git-svn.txt: replace .git with $GIT_DIR
  git-svn.txt: reword description of gc command
  git-svn.txt: fix AsciiDoc formatting error
  git-svn: fix signed commit parsing