Merge branch 'maint-1.6.0' into maint-1.6.1

* maint-1.6.0:
Fix bash completion in path with spaces
bash completion: only show 'log --merge' if merging
git-tag(1): add hint about commit messages
Documentation: update graph api example.

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

diff --cc contrib/completion/git-completion.bash
Simple merge