git-branch: document new --no-abbrev option

Add the new --no-abbrev option to the man page for the git-branch command.
Signed-off-by: NJulian Phillips <julian@quantumfyre.co.uk>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/git-branch.txt

@@ -8,7 +8,8 @@ git-branch - List, create, or delete branches
 SYNOPSIS
 --------
 [verse]
-'git-branch' [--color | --no-color] [-r | -a] [-v [--abbrev=<length>]]
+'git-branch' [--color | --no-color] [-r | -a]
+	   [-v [--abbrev=<length> | --no-abbrev]]
 'git-branch' [-l] [-f] <branchname> [<start-point>]
 'git-branch' (-m | -M) [<oldbranch>] <newbranch>
 'git-branch' (-d | -D) [-r] <branchname>...
@@ -80,6 +81,9 @@ OPTIONS
 	Alter minimum display length for sha1 in output listing,
 	default value is 7.
 
+--no-abbrev::
+	Display the full sha1s in output listing rather than abbreviating them.
+
 <branchname>::
 	The name of the branch to create or delete.
 	The new branch name must pass all checks defined by