This works similarly to `svn update` or 'git-pull' except that
it preserves linear history with 'git-rebase' instead of
-'git-merge' for ease of dcommiting with 'git-svn'.
+'git-merge' for ease of dcommitting with 'git-svn'.
This accepts all options that 'git-svn fetch' and 'git-rebase'
accept. However, '--fetch-all' only fetches from the current