patch from https://bugs.launchpad.net/virtualenv/+bug/550545 to add activate.csh to virtualenv

virtualenv activate.csh

--- a/virtualenv.py
+++ b/virtualenv.py
@@ -867,5 +867,5 @@
             files['activate'] = ACTIVATE_SH
     else:
-        files = {'activate': ACTIVATE_SH}
+        files = {'activate': ACTIVATE_SH, 'activate.csh': ACTIVATE_CSH}
     files['activate_this.py'] = ACTIVATE_THIS
     for name, content in files.items():
@@ -1426,4 +1426,29 @@
 """.decode("base64").decode("zlib")
 
+##file activate.csh
+ACTIVATE_CSH = """\
+# This file must be used with "source bin/activate" *from csh*
+# you cannot run it directly
+
+alias deactivate-nondestructive 'setenv PATH "$_OLD_VIRTUAL_PATH"; unsetenv _OLD_VIRTUAL_PATH; set prompt = "$_OLD_VIRTUAL_PROMPT"; unsetenv _OLD_VIRTUAL_PROMPT; unsetenv VIRTUAL_ENV'
+alias deactivate 'deactivate-nondestructive; unalias deactivate-nondestructive; unalias deactivate'
+if ($?_OLD_VIRTUAL_PATH) then
+    if ("$_OLD_VIRTUAL_PATH" != "") then
+        deactivate-nondestructive
+    endif
+endif
+
+setenv VIRTUAL_ENV "__VIRTUAL_ENV__"
+
+setenv _OLD_VIRTUAL_PATH "$PATH"
+setenv PATH "$VIRTUAL_ENV/bin:$PATH"
+
+if (! $?prompt) then
+    set prompt = "% "
+endif
+setenv _OLD_VIRTUAL_PROMPT "$prompt"
+set prompt = "($VIRTUAL_ENV:t)$prompt"
+"""
+
 ##file activate.bat
 ACTIVATE_BAT = """