[PATCH] format-patch: Generate a newline between the subject header and the message body

format-patch previously didn't generate a newline after a subject. This 
caused the diffstat to not be displayed in messages with only one line 
for the commit message.
This patch fixes this by adding a newline after the headers if a body 
hasn't been added.
Signed-off-by: Robert Shearman <redacted>
---
  commit.c |   11 +++++++++--
  1 files changed, 9 insertions(+), 2 deletions(-)