Document git-blame triple -C option

Lift the explanation of -CCC option in the source to the documentation.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/blame-options.txt

@@ -98,8 +98,10 @@ commit.
 	files that were modified in the same commit.  This is
 	useful when you reorganize your program and move code
 	around across files.  When this option is given twice,
-	the command additionally looks for copies from all other
+	the command additionally looks for copies from other
-	files in the parent for the commit that creates the file.
+	files in the commit that creates the file. When this
+	option is given three times, the command additionally
+	looks for copies from other files in any commit.
 +
 <num> is optional but it is the lower bound on the number of
 alphanumeric characters that git must detect as moving

Documentation/git-blame.txt

@@ -9,7 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git blame' [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-p] [-w] [--incremental] [-L n,m]
-            [-S <revs-file>] [-M] [-C] [-C] [--since=<date>]
+	    [-S <revs-file>] [-M] [-C] [-C] [-C] [--since=<date>]
 	    [<rev> | --contents <file> | --reverse <rev>] [--] <file>
 
 DESCRIPTION