commits: skip b4 cover-letter commit

They are empty, no need to validate them, and checkpatch would complain
about them.

Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

Author: matttbe

entrypoint.sh

@@ -162,6 +162,11 @@ is_commit_skipped() { local commit curr
 		fi
 	done
 
+	# Skip empty commits used by b4
+	if git log -1 HEAD | grep -q "^\s\+--- b4-submit-tracking ---$"; then
+		return 0
+	fi
+
 	return 1
 }