Question about about a trivial merge conflict that git should resolve alone

From: Francis Moreau <francis.moro@gmail.com>
Date: Oct 23, 2015, 13:07 UTC
Message-ID: <CAC9WiBj7Vwfjzbik7+d9cxpS=m+_s-CViJ3b4fKAzYQ4ixXfiw@mail.gmail.com>

Hi,

I have a simple merge conflict use case:

$ mkdir foo $ cd foo/ $ git init $ echo line1 > a $ git add . $ git commit -q -m init $ echo line2 >>a $ git commit -a -q -m "add line2" $ git checkout -b foo HEAD~1 $ git cherry-pick -x master $ echo line3 >>a $ git stage a $ git commit -q -m "add line3" $ git checkout master $ git merge foo $ git diff diff --cc a index c0d0fb4,83db48f..0000000

--- a/a
+++ b/a
@@@ -1,2 -1,3 +1,6 @@@
line1
line2
++<<<<<<< HEAD
++=======
+ line3
++>>>>>>> foo

Why does git think there's a conflict here since the "line2" string
was added in both branch by the same commit ?

Thanks.

-- 
Francis