revisions.txt: mention <rev>~ form

In revisions.txt, the '<rev>^' form is mentioned but the '<rev>~' form
is missing. Although both forms are essentially equivalent (they each
get the first parent of the specified revision), we should mention the
latter for completeness. Make this change.

While we're at it, the brief form of '<rev>^' makes it seem as if no
numerical argument is accepted. Update documentation to make it obvious
that an optional numerical argument is accepted.

Signed-off-by: Denton Liu <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Denton-L

Documentation/revisions.txt

@@ -131,15 +131,17 @@ from one location and push to another. In a non-triangular workflow,
 This suffix is also accepted when spelled in uppercase, and means the same
 thing no matter the case.
 
-'<rev>{caret}', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
+'<rev>{caret}[<n>]', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
   A suffix '{caret}' to a revision parameter means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
   '<rev>{caret}'
   is equivalent to '<rev>{caret}1').  As a special rule,
   '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
   object name of a tag object that refers to a commit object.
 
-'<rev>{tilde}<n>', e.g. 'master{tilde}3'::
+'<rev>{tilde}[<n>]', e.g. 'HEAD{tilde}, master{tilde}3'::
+  A suffix '{tilde}' to a revision parameter means the first parent of
+  that commit object.
   A suffix '{tilde}<n>' to a revision parameter means the commit
   object that is the <n>th generation ancestor of the named
   commit object, following only the first parents.  I.e. '<rev>{tilde}3' is