Change the naming scheme of virtualenv

New property has been added as discussed as
https://github.com/kennethreitz/pipenv/pull/238#discussion_r102049269

    project.virtualenv_name

It'll be '<sanitized-name>-<hash>' where <sanitized-name> is a project
name without whitespaces, and hash is base64-encoded sha256 of pipfile
location.

For example, if the pipfile was located at '/home/user/MY_PROJECT/Pipfile',
the 'virtualenv_name' will be 'my-project-wyUfYPqE'.

Closes #228

References:
  https://github.com/kennethreitz/pipenv/issues/228
  https://github.com/kennethreitz/pipenv/pull/238

pipenv/cli.py

@@ -321,7 +321,7 @@ def do_create_virtualenv(three=None, python=None):
         cmd = ['virtualenv', project.virtualenv_location, '--prompt=({0})'.format(project.name)]
     else:
         # Default: use pew.
-        cmd = ['pew', 'new', project.name, '-d']
+        cmd = ['pew', 'new', project.virtualenv_name, '-d']
 
     # Pass a Python version to virtualenv, if needed.
     if python:
@@ -891,7 +891,7 @@ def shell(three=None, python=False, compat=False, shell_args=None):
     # Standard (properly configured shell) mode:
     else:
         cmd = 'pew'
-        args = ["workon", project.name]
+        args = ["workon", project.virtualenv_name]
 
     # Grab current terminal dimensions to replace the hardcoded default
     # dimensions of pexpect

pipenv/project.py

@@ -1,6 +1,9 @@
 # -*- coding: utf-8 -*-
 import json
 import os
+import re
+import base64
+import hashlib
 
 import pipfile
 import toml
@@ -37,6 +40,23 @@ class Project(object):
     def virtualenv_exists(self):
         return os.path.isdir(self.virtualenv_location)
 
+    @property
+    def virtualenv_name(self):
+        # Replace dangerous characters into '_'
+        #
+        # References:
+        #   https://www.gnu.org/software/bash/manual/html_node/Double-Quotes.html
+        #   http://www.tldp.org/LDP/abs/html/special-chars.html#FIELDREF
+        sanitized = re.sub(r'[ $`!*@"\\\r\n\t]', '_', self.name)
+
+        # Hash the full path of the pipfile
+        hash = hashlib.sha256(self.pipfile_location.encode()).digest()[:6]
+        encoded_hash = base64.urlsafe_b64encode(hash).decode()
+
+        # If the pipfile was located at '/home/user/MY_PROJECT/Pipfile',
+        # the name of its virtualenv will be 'my-project-wyUfYPqE'
+        return sanitized + '-' + encoded_hash
+
     @property
     def virtualenv_location(self):
 
@@ -46,7 +66,7 @@ class Project(object):
 
         # The user wants the virtualenv in the project.
         if not PIPENV_VENV_IN_PROJECT:
-            c = delegator.run('pew dir "{0}"'.format(self.name))
+            c = delegator.run('pew dir "{0}"'.format(self.virtualenv_name))
             loc = c.out.strip()
         # Default mode.
         else:

tests/test_project.py

@@ -1,3 +1,6 @@
+from hashlib import sha256
+from base64 import urlsafe_b64encode
+
 import delegator
 
 import pipenv.project
@@ -6,9 +9,13 @@ class TestProject():
 
     def test_project(self):
         proj = pipenv.project.Project()
+        hash = urlsafe_b64encode(
+            sha256(proj.pipfile_location.encode()).digest()[:6]).decode()
+
         assert proj.name == 'pipenv'
         assert proj.pipfile_exists
         assert proj.virtualenv_exists
+        assert proj.virtualenv_name == 'pipenv-' + hash
 
     def test_proper_names(self):
         proj = pipenv.project.Project()