A random collection of style fixes and minor doc updates.
* fc/trivial:
setup: trivial style fixes
run-command: trivial style fixes
diff: trivial style fix
revision: trivial style fixes
pretty: trivial style fix
describe: trivial style fixes
transport-helper: trivial style fix
sha1-name: trivial style cleanup
branch: trivial style fix
revision: add missing include
doc/pull: clarify the illustrations
t: replace pulls with merges
merge: simplify ff-only option