+To summarize:
+
+'<rev>'::
+ Include commits that are reachable from (i.e. ancestors of)
+ <rev>.
+
+'{caret}<rev>'::
+ Exclude commits that are reachable from (i.e. ancestors of)
+ <rev>.
+
+'<rev1>..<rev2>'::
+ Include commits that are reachable from <rev2> but exclude
+ those that are reachable from <rev1>.
+
+'<rev1>\...<rev2>'::
+ Include commits that are reachable from either <rev1> or
+ <rev2> but exclude those that are reachable from both.
+
+'<rev>{caret}@', e.g. 'HEAD{caret}@'::
+ A suffix '{caret}' followed by an at sign is the same as listing
+ all parents of '<rev>' (meaning, include anything reachable from
+ its parents, but not the commit itself).
+
+'<rev>{caret}!', e.g. 'HEAD{caret}!'::
+ A suffix '{caret}' followed by an exclamation mark is the same
+ as giving commit '<rev>' and then all its parents prefixed with
+ '{caret}' to exclude them (and their ancestors).
+