[#439] Append a hash to minified file names.

This will enforce browsers to retrieve again the file when the hash
changes, making sure users don't use old versions of the JS code.

The minify script is changed in several ways, in addition to
calculating and appending the hash to the file name:

* To revert previous minification, we now use git reset --hard. It's
  dangerous but prevents the regexp logic from getting too wild.

* We now loop through the php files for every js file, making the
  script much less efficient. Again, this is done to simplify regexp
  logic.

* Explicitly delete source map files from previous minification, to
  prevent maps with different hashes to pile up.

Makefile

@@ -39,21 +39,25 @@ help:
 	rm footer
 
 minify:
+	# WARNING: this will remove any unstaged changes! Do not run on a development directory
 	for i in `find -name "*.min.js" -not -path "*web/vuejs/*"`; do rm $$i; done
-	for i in `find -name "*.js" -not -path "*web/vuejs/*"` ; do \
+	for i in `find -name "*.min.js.map" -not -path "*web/vuejs/*"`; do rm $$i; done
+	#revert any previous minification changes
+	git reset --hard HEAD
+	for i in `find -name "*.js" -not -path "*web/vuejs/*" -not -path "*vendor*"` ; do \
 	  #extract file name to be used in the uglify output \
 	  FILE=`basename -s .js $$i`; \
 	  DIR=`dirname $$i`; \
+	  HASH=`md5sum $$i | awk '{ print $$1 }'`; \
 	  cd $$DIR; \
-	  uglifyjs $${FILE}.js --output $${FILE}.min.js \
-	      --source-map "filename=$${FILE}.min.js.map" -c -m; \
+	  uglifyjs $${FILE}.js --output $${FILE}.$${HASH}.min.js \
+	      --source-map "filename='$${FILE}.$${HASH}.min.js.map'" -c -m; \
 	  cd -; \
-	  done
-	for i in `find web -name "*.php" -not -path "*web/holiday*"`; do \
-	  #revert any previous minification changes \
-	  sed 's/<script src="\(.*\).min.js">/<script src="\1.js">/' $$i > tmp; \
-	  #modify script tags to link the minified file \
-	  sed 's/<script src="\(.*\).js">/<script src="\1.min.js">/' tmp > $$i; \
+	  for j in `find web -name "*.php"`; do \
+	    #modify script tags to link the minified file \
+	    sed "s/<script src=\"\(.*\)$${FILE}.js\">/<script src=\"\1$${FILE}.$${HASH}.min.js\">/" $$j > tmp; \
+	    cp tmp $$j; \
+	    done \
 	  done
 	rm tmp