Merge branch 'dl/rev-tilde-doc-clarify'

Docfix.

* dl/rev-tilde-doc-clarify:
revisions.txt: remove ambibuity between <rev>:<path> and :<path>
revisions.txt: mention <rev>~ form
revisions.txt: mark optional rev arguments with []
revisions.txt: change "rev" to "<rev>"

diff --cc Documentation/revisions.txt
Simple merge