Merge branch 'mm/am-c-doc' into maint

The configuration variable 'mailinfo.scissors' was hard to
discover in the documentation.

* mm/am-c-doc:
Documentation/git-am.txt: mention mailinfo.scissors config variable
Documentation/config.txt: document mailinfo.scissors

diff --cc Documentation/config.txt
Simple merge

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