blame documentation: -M/-C notice copied lines as well as moved ones

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/blame-options.txt

@@ -79,22 +79,23 @@ of lines before or after the line given by <start>.
 	of the --date option at linkgit:git-log[1].
 
 -M|<num>|::
-	Detect moving lines in the file as well.  When a commit
-	moves a block of lines in a file (e.g. the original file
-	has A and then B, and the commit changes it to B and
-	then A), the traditional 'blame' algorithm typically blames
-	the lines that were moved up (i.e. B) to the parent and
-	assigns blame to the lines that were moved down (i.e. A)
-	to the child commit.  With this option, both groups of lines
-	are blamed on the parent.
+	Detect moved or copied lines within a file. When a commit
+	moves or copies a block of lines (e.g. the original file
+	has A and then B, and the commit changes it to B and then
+	A), the traditional 'blame' algorithm notices only half of
+	the movement and typically blames the lines that were moved
+	up (i.e. B) to the parent and assigns blame to the lines that
+	were moved down (i.e. A) to the child commit.  With this
+	option, both groups of lines are blamed on the parent by
+	running extra passes of inspection.
 +
 <num> is optional but it is the lower bound on the number of
 alphanumeric characters that git must detect as moving
 within a file for it to associate those lines with the parent
 commit.
 
 -C|<num>|::
-	In addition to `-M`, detect lines copied from other
+	In addition to `-M`, detect lines moved or copied from other
 	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,