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

@@ -79,14 +79,15 @@ 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
+	Detect moved or copied lines within a file. When a commit
-	moves a block of lines in a file (e.g. the original file
+	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
+	has A and then B, and the commit changes it to B and then
-	then A), the traditional 'blame' algorithm typically blames
+	A), the traditional 'blame' algorithm notices only half of
-	the lines that were moved up (i.e. B) to the parent and
+	the movement and typically blames the lines that were moved
-	assigns blame to the lines that were moved down (i.e. A)
+	up (i.e. B) to the parent and assigns blame to the lines that
-	to the child commit.  With this option, both groups of lines
+	were moved down (i.e. A) to the child commit.  With this
-	are blamed on the parent.
+	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
@@ -94,7 +95,7 @@ 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,