Merge branch 'maint'

* maint:
t/t9001-send-email.sh: fix stderr redirection in 'Invalid In-Reply-To'
Clarify and extend the "git diff" format documentation
git-show-ref.txt: clarify the pattern matching
documentation: git-config minor cleanups
Update test script annotate-tests.sh to handle missing/extra authors

diff --cc Documentation/config.txt
Simple merge

diff --cc t/t9001-send-email.sh
Simple merge