Refer users to git-rev-parse for revision specification syntax.

The revision specification syntax (sometimes referred to as
SHA1-expressions) is accepted almost everywhere in Git by
almost every tool.  Unfortunately it is only documented in
git-rev-parse.txt, and most users don't know to look there.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-cherry-pick.txt

@@ -19,6 +19,8 @@ OPTIONS
 -------
 <commit>::
 	Commit to cherry-pick.
+	For a more complete list of ways to spell commits, see
+	"SPECIFYING REVISIONS" section in gitlink:git-rev-parse[1].
 
 -e|--edit::
 	With this option, `git-cherry-pick` will let you edit the commit

Documentation/git-diff.txt

@@ -47,6 +47,9 @@ Just in case if you are doing something exotic, it should be
 noted that all of the <commit> in the above description can be
 any <tree-ish>.
 
+For a more complete list of ways to spell <commit>, see
+"SPECIFYING REVISIONS" section in gitlink:git-rev-parse[1].
+
 
 OPTIONS
 -------

Documentation/git-format-patch.txt

@@ -20,7 +20,9 @@ DESCRIPTION
 Prepare each commit between <since> and <until> with its patch in
 one file per commit, formatted to resemble UNIX mailbox format.
 If ..<until> is not specified, the head of the current working
-tree is implied.
+tree is implied.  For a more complete list of ways to spell
+<since> and <until>, see "SPECIFYING REVISIONS" section in
+gitlink:git-rev-parse[1].
 
 The output of this command is convenient for e-mail submission or
 for use with gitlink:git-am[1].

Documentation/git-log.txt

@@ -34,6 +34,9 @@ include::pretty-formats.txt[]
 	Show only commits between the named two commits.  When
 	either <since> or <until> is omitted, it defaults to
 	`HEAD`, i.e. the tip of the current branch.
+	For a more complete list of ways to spell <since>
+	and <until>, see "SPECIFYING REVISIONS" section in
+	gitlink:git-rev-parse[1].
 
 -p::
 	Show the change the commit introduces in a patch form.

Documentation/git-revert.txt

@@ -19,6 +19,8 @@ OPTIONS
 -------
 <commit>::
 	Commit to revert.
+	For a more complete list of ways to spell commit names, see
+	"SPECIFYING REVISIONS" section in gitlink:git-rev-parse[1].
 
 -e|--edit::
 	With this option, `git-revert` will let you edit the commit

Documentation/git-show.txt

@@ -32,6 +32,8 @@ OPTIONS
 -------
 <object>::
 	The name of the object to show.
+	For a more complete list of ways to spell object names, see
+	"SPECIFYING REVISIONS" section in gitlink:git-rev-parse[1].
 
 include::pretty-formats.txt[]
 

Documentation/gitk.txt

@@ -47,6 +47,8 @@ frequently used options.
 	meaning show from the given revision and back, or it can be a range in
 	the form "'<from>'..'<to>'" to show all revisions between '<from>' and
 	back to '<to>'. Note, more advanced revision selection can be applied.
+	For a more complete list of ways to spell object names, see
+	"SPECIFYING REVISIONS" section in gitlink:git-rev-parse[1].
 
 <path>::