Enumerate revision range specifiers in the documentation

It was a bit hard to learn how <rev>^@, <rev>^! and various other
forms of range specifiers are used, because they were discussed
mostly in the prose part of the documentation, unlike various forms
of extended SHA-1 expressions that are listed in an enumerated list.

Also add a few more examples showing use of <rev>, <rev>..<rev> and
<rev>^! forms, stolen from a patch by Max Horn.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/revisions.txt

@@ -218,13 +218,44 @@ and its parent commits exist.  The 'r1{caret}@' notation means all
 parents of 'r1'.  'r1{caret}!' includes commit 'r1' but excludes
 all of its parents.
 
+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).
+
 Here are a handful of examples:
 
    D                G H D
    D F              G H I J D F
    ^G D             H D
    ^D B             E I J F B
+   B..C             C
    B...C            G H D E B C
    ^D B C           E I J F B C
+   C                I J F C
    C^@              I J F
+   C^!              C
    F^! D            G H D F