create-pull-request: handle empty ODIR

In some situations you might end-up with an empty ODIR (pull-xx/). The
most common reason is that you have applied your patches on 'master'
branch (or you are by mistake standing on the 'master' branch),
this will result in the default behavior that 'git format-patch'
will try to diff master..master.

Solve this by aborting the script with a proper error code and message
if ODIR is empty after the 'git format-patch' call (that is expected
to generate the cover-letter and patches).

(From OE-Core rev: 5ef9249bbae4f08eb9b981d10f31bd3348449c82)

Signed-off-by: Petter Mabäcker <petter@technux.se>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/create-pull-request

@@ -185,6 +185,14 @@ fi
 # Generate the patches and cover letter
 git format-patch $extraopts -M40 --subject-prefix="$PREFIX" -n -o $ODIR --thread=shallow --cover-letter $RELATIVE_TO..$COMMIT_ID > /dev/null
 
+if [ -z "$(ls -A $ODIR 2> /dev/null)" ]; then
+    echo "ERROR: $ODIR is empty, no cover letter and patches was generated!"
+    echo "       This is most likely due to that \$RRELATIVE_TO..\$COMMIT_ID"
+    echo "       ($RELATIVE_TO..$COMMIT_ID) don't contain any differences."
+    rmdir $ODIR
+    exit 1
+fi
+
 [ -n "$RELDIR" ] && cd $pdir
 
 # Customize the cover letter