[BUGS] test failure in t4014-format-patch.sh with master

Hello,

While trying to wrote a test for git, I discover that there is a test failure in master on my computer:

$ ./t4014-format-patch.sh
[....]
* FAIL 8: replay did not screw up the log message

 git cat-file commit rebuild-1 | grep "^Side .* with .* backslash-n"

It seem that now, somewhere a \n has been interpreted as a newline.

Bisecting point the problem to the 2e6e3e82 commit "git-am: cope better with an empty Subject: line"