extract function to check if file exists

this will need to be extended to also check for the existance of files
inside of jars

src/clj_jtwig/core.clj

@@ -73,7 +73,7 @@
 ; this function really only exists so i can easily change the exception type / message in the future
 ; since this file-exists check is needed in a few places
 (defn- err-if-no-file [^File file]
-  (if-not (.exists file)
+  (if-not (exists? file)
     (throw (new FileNotFoundException (str "Template file \"" file "\" not found.")))))
 
 (defn- cache-compiled-template! [^File file create-fn]

src/clj_jtwig/utils.clj

@@ -9,6 +9,12 @@
       ; the path of a file inside a jar looks something like "jar:file:/path/to/file.jar!/path/inside/jar/to/file"
       (.contains "jar!")))
 
+(defn exists? [^File file]
+  (if (inside-jar? file)
+    ;; TODO: can't use File.exists() for this
+    true
+    (.exists file)))
+
 (defn get-file-last-modified [^File file]
   (if (inside-jar? file)
     0