Makefile: add check target, run it on Travis

Author: blueyed

.travis.yml

@@ -27,3 +27,4 @@ script:
   - which -a vim
   - vim --cmd version --cmd quit
   - test/run.sh
+  - make check

Makefile

@@ -1,9 +1,15 @@
 VIM_COMPILER:=vim -N --cmd 'set rtp+=.' -c q -u
+COMPILED_FILES:=js/vimlparser.js py/vimlparser.py
 
-all: js/vimlparser.js py/vimlparser.py
+all: $(COMPILED_FILES)
 
 js/vimlparser.js: autoload/vimlparser.vim js/jscompiler.vim js/vimlfunc.js
 	$(VIM_COMPILER) js/jscompiler.vim
 
 py/vimlparser.py: autoload/vimlparser.vim py/pycompiler.vim py/vimlfunc.py
 	$(VIM_COMPILER) py/pycompiler.vim
+
+check: all
+	git diff --exit-code $(COMPILED_FILES) || { \
+	  echo 'Compiled files were updated, but should have been committed.'; \
+	  exit 1; }