component/macros/virtual-env: Add script chaining

Now, with the `chain` option, you can source a chain of activate script
created by the macro.

In addition, the `deactivate` function will return to the initial environment.

component/macros/virtual-env.cfg

@@ -2,6 +2,8 @@
 extends =
 	../pygolang/buildout.cfg
 
+parts =
+
 [virtual-env-base]
 recipe = slapos.recipe.build
 name = ${:_buildout_section_name_}
@@ -12,6 +14,7 @@ init =
   name = options['name']
   eggs = options.get('eggs')
   self.message = options.get('message')
+  self.chain = options.get('chain')
   environment = options.get('environment')
   scripts = options.get('scripts')
 
@@ -74,14 +77,20 @@ init =
 install =
   message = ""
   if self.message:
-    message = "\n  echo " + "\n  echo ".join(
+    message = "echo " + "\n  echo ".join(
       "%r" % line for line in self.message.splitlines())
     message += "\n  echo \'\'"
 
+  chain = ""
+  if self.chain:
+    chain = "source " + "\n  source ".join(
+      "%r" % line for line in self.chain.splitlines())
+
   with open(location, "w") as f:
     f.write(options['template'] % {
       "env": " ".join("%s %s" % (k, v) for k, v in self.env.items()),
       "message": message,
+      "chain": chain,
     })
 
 # Template virtual env for bash shell in posix
@@ -89,24 +98,47 @@ install =
 template =
   if type deactivate > /dev/null 2>&1
   then
-    echo "deactivate current environment first"
+    export _OLD_PARAM=( "$@")
+    set %(env)s
+    while [ "$1" ]; do
+      if ! ( echo $_LIST_OLD_VENV | grep $1 ) > /dev/null 2>&1
+      then
+        eval "export _OLD_VENV_$1=\$$1"
+        eval "export _LIST_OLD_VENV=\"$1 \$_LIST_OLD_VENV\""
+      fi
+      eval "export $1=\"$2\""
+      shift
+      shift
+    done
+    if [[ -n "$_OLD_PARAM" ]]; then
+      set "$${_OLD_PARAM[@]}"
+    fi
+    unset _OLD_PARAM
+    %(chain)s
+    %(message)s
   else
     deactivate () {
-      set %(env)s
+      set $_LIST_OLD_VENV
       while [ "$1" ]; do
         eval "if [ \"\$_OLD_VENV_$1\" ]; then $1=\$_OLD_VENV_$1; else unset $1; fi; unset \$_OLD_VENV_$1"
         shift
-        shift
       done
       unset -f deactivate
+      unset _LIST_OLD_VENV
     }
-
+    export _OLD_PARAM=( "$@" )
     set %(env)s
     while [ "$1" ]; do
       eval "_OLD_VENV_$1=\$$1"
       eval "export $1=\"$2\""
+      eval "export _LIST_OLD_VENV=\"$1 \$_LIST_OLD_VENV\""
       shift
       shift
     done
+    if [[ -n "$_OLD_PARAM" ]]; then
+      set "$${_OLD_PARAM[@]}"
+    fi
+    unset _OLD_PARAM
+    %(chain)s
     %(message)s
   fi