git blame -M seems not to work as expected

Hi Folks!

I've posed this question already on stackoverflow and on Google Groups - without any (satisfying) answer. So maybe you can help me to understand the behavior of git blame -M.

First I commit the following file(file.cpp):

void func1(){return;}[CR][LF]
int func2(){return 23;}[CR][LF]    

Then I modify it by moving what was in the first line and adding something new instead:

float newFunc(){return 23.0;}[CR][LF]
int func2(){return 23;}[CR][LF]
[CR][LF]
[CR][LF]
void func1(){return;}[CR][LF]
 
The log now looks as follows:

git log --oneline -2

18c670f modified file.cpp
92b4186 added file.cpp
 
Now I run blame:

git blame -s -w -M file.cpp
18c670fa 1) float newFunc(){return 23.0;}
92b4186d 2) int func2(){return 23;}
18c670fa 3)
18c670fa 4)
18c670fa 5) void func1(){return;}
 
I wonder why the line containing func1() isn't recognized as moved. I've tried to reduce the number of required characters (i.e. -M4 etc.). Furthermore spaces should not matter because of the -w option.

On the other hand, when I move float newFunc(){return 23.0;} from line 1 to line 6 (which was empty before) in the subsequent commit, git blame -M correctly recognizes that it originates from commit 18c670fa even though it firstly appeared in line 6 only in the current commit. 

So what's the reason for this seemingly inconsequent behavior? As far as I understand the documentation, both movements should be recognized. It's very important for us to correctly understand the behavior of git blame -M since we are about to add some code analysis logic on top of git blame. 

Thanks in advance
Konstantin