Merge branch 'tr/doc-tt' into maint

The documentation set has been updated so that literal commands,
configuration variables and environment variables are consistently
typeset in fixed-width font and bold in manpages.

* tr/doc-tt:
doc: change configuration variables format
doc: more consistency in environment variables format
doc: change environment variables format
doc: clearer rule about formatting literals

diff --cc Documentation/config.txt
Simple merge

diff --cc Documentation/diff-config.txt
Simple merge

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

diff --cc Documentation/git-format-patch.txt
Simple merge

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

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

diff --cc Documentation/git-p4.txt
Simple merge

diff --cc Documentation/git-send-email.txt
Simple merge

diff --cc Documentation/git.txt
Simple merge

diff --cc Documentation/pretty-options.txt
Simple merge