Adapt htmlize installer for the case of existing git submodule

tools/install_htmlize.sh

@@ -2,8 +2,25 @@
 #
 # Installs the htmlize Emacs plugin
 
-${abs_srcdir}/tools/missing git clone "https://github.com/TREX-CoE/emacs-htmlize"
-mv emacs-htmlize/htmlize.el $1
-rm -rf emacs-htmlize
+readonly HTMLIZE_EL=$1
 
+# If the file already present - exit the script
+if [ -f ${HTMLIZE_EL} ]
+then
+	exit 0	
+fi
+
+DOC_ROOT=${HTMLIZE_EL%/*}
+readonly EMACS_HTMLIZE=${DOC_ROOT}/emacs-htmlize/htmlize.el
+
+# Case 1: submodule cloned but htmlize.el is absent in DOC_ROOT
+if [ -f ${EMACS_HTMLIZE} ]
+then
+	cp ${EMACS_HTMLIZE} ${HTMLIZE_EL}
+else
+# Case 2: submodule has not been cloned
+	${abs_srcdir}/tools/missing git clone "https://github.com/TREX-CoE/emacs-htmlize"
+	mv emacs-htmlize/htmlize.el ${HTMLIZE_EL}
+	rm -rf emacs-htmlize
+fi