Merge branch 'jk/pretty-G-format-fixes'

* jk/pretty-G-format-fixes: move "%G" format test from t7510 to t6006 pretty: avoid reading past end-of-string with "%G" t7510: check %G* pretty-format output t7510: test a commit signed by an unknown key t7510: use consistent &&-chains in loop t7510: stop referring to master in later tests