[pathmunge] added function to prevent duplicates in PATH variable

lib/helpers.bash

@@ -361,3 +361,21 @@ all_groups ()
     cat $file | sort | uniq
     rm $file
 }
+
+if ! type pathmunge > /dev/null 2>&1
+then
+  function pathmunge () {
+    _about 'prevent duplicate directories in you PATH variable'
+    _group 'lib helpers'
+    _example 'pathmunge /path/to/dir is equivalent to PATH=/path/to/dir:$PATH'
+    _example 'pathmunge /path/to/dir after is equivalent to PATH=$PATH:/path/to/dir'
+
+    if ! [[ $PATH =~ (^|:)$1($|:) ]] ; then
+      if [ "$2" = "after" ] ; then
+        export PATH=$PATH:$1
+      else
+        export PATH=$1:$PATH
+      fi
+    fi
+  }
+fi