.travis.yml: Detect if 'make update' updated something
If it did, it really is something that should be checked in, and should
therefore make a CI build fail.
@@ -184,7 +184,8 @@ script:
- if [ -n "$DESTDIR" ]; then
cd _build;
fi
- - $make update
+ - $make update;
+ git diff --quiet
- if [ -n "$CHECKDOCS" ]; then
$make doc-nits;
fi
