component/macros/virtual-env: allows you to create a custom environment

The `message` option allows to write a message that will be displayed when sourcing the script.

The `environment` option allows you to write your own environment variables for the virtual environment.
To use it:
environment =
  <env-name> = <env-value>

component/macros/virtual-env.cfg

@@ -10,26 +10,25 @@ init =
   from zc.buildout.easy_install import working_set
   import os
   name = options['name']
-  eggs = options['eggs']
-  try:
-    scripts = "scripts = " + options['scripts']
-  except KeyError:
-    scripts = ""
+  eggs = options.get('eggs')
+  self.message = options.get('message')
+  environment = options.get('environment')
+  scripts = options.get('scripts')
 
-  self.buildout.parse("""
+  eggs_template = """
   [.%(name)s.install-eggs]
   recipe = zc.recipe.egg
-  eggs = %(eggs)s
+  eggs =
+    %(eggs)s
   %(scripts)s
 
   [.%(name)s.install-interpreter]
   <= python-interpreter
-  eggs += %(eggs)s
-  """ % locals())
+  eggs +=
+    %(eggs)s
+  """
 
-  if is_true(options.get('default-instance')):
-    cookbook = "{slapos-cookbook:recipe}"
-    self.buildout.parse("""
+  instance_template = """
   [.%(name)s.instance]
   recipe = slapos.recipe.template
   output = ${buildout:directory}/instance.cfg
@@ -44,30 +43,70 @@ init =
     [publish]
     recipe = slapos.cookbook:publish
     activate-script = %(location)s
-    """ % locals())
+  """
+
+  if eggs:
+    self.buildout.parse(eggs_template % {
+      "eggs": "\n  ".join(e.strip() for e in eggs.splitlines()),
+      "name": name,
+      "scripts": "scripts = " + scripts if scripts else "",
+    })
+
+  if is_true(options.get('default-instance')):
+    self.buildout.parse(instance_template % {
+      "cookbook": "{slapos-cookbook:recipe}",
+      "location": location,
+      "name": name,
+    })
+
+  env = {
+    "PATH": self.buildout['buildout']['bin-directory'] + ":\$PATH",
+    "PS1": "\"(" + self.name + ") \$PS1\"",
+  }
+
+  if environment:
+    for line in environment.splitlines():
+      key, value = line.split("=", 1)
+      env[key.strip()] = value.strip()
+
+  self.env = env
 
 install =
+  message = ""
+  if self.message:
+    message = "\n  echo " + "\n  echo ".join(
+      "%r" % line for line in self.message.splitlines())
+    message += "\n  echo \'\'"
+
   with open(location, "w") as f:
     f.write(options['template'] % {
-      "path" : self.buildout['buildout']['bin-directory'],
-      "name" : self.name,
+      "env": " ".join("%s %s" % (k, v) for k, v in self.env.items()),
+      "message": message,
     })
 
 # Template virtual env for bash shell in posix
 [virtual-env-base:posix]
 template =
+  if type deactivate > /dev/null 2>&1
+  then
+    echo "deactivate current environment first"
+  else
     deactivate () {
-    set PATH PS1
+      set %(env)s
       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
     }
 
-
-  VENV_PATH=%(path)s
-  _OLD_VENV_PATH=$PATH
-  _OLD_VENV_PS1=$PS1
-  PATH=$VENV_PATH:$PATH
-  PS1='(%(name)s) '$PS1
+    set %(env)s
+    while [ "$1" ]; do
+      eval "_OLD_VENV_$1=\$$1"
+      eval "export $1=\"$2\""
+      shift
+      shift
+    done
+    %(message)s
+  fi