Resolve Pipfile location for hash caculation

This should prevent the lookup loop most of the time, especially for new
virtualenvs created from now on.

pipenv/project.py

@@ -11,11 +11,15 @@ import hashlib
 
 import contoml
 import delegator
-from pipenv.vendor.first import first
 import pipfile
 import pipfile.api
 import toml
 
+try:
+    import pathlib
+except ImportError:
+    import pathlib2 as pathlib
+
 from pip9 import ConfigOptionParser
 from .cmdparse import Script
 from .utils import (
@@ -43,12 +47,19 @@ from .environments import (
     PIPENV_PYTHON,
 )
 
+
+def _normalized(p):
+    if p is None:
+        return None
+    return normalize_drive(str(pathlib.Path(p).resolve()))
+
+
 if PIPENV_PIPFILE:
     if not os.path.isfile(PIPENV_PIPFILE):
         raise RuntimeError('Given PIPENV_PIPFILE is not found!')
 
     else:
-        PIPENV_PIPFILE = normalize_drive(os.path.abspath(PIPENV_PIPFILE))
+        PIPENV_PIPFILE = _normalized(PIPENV_PIPFILE)
 # (path, file contents) => TOMLFile
 # keeps track of pipfiles that we've seen so we do not need to re-parse 'em
 _pipfile_cache = {}
@@ -235,20 +246,32 @@ class Project(object):
             name = self._sanitize(name)
             hash = hashlib.sha256(location.encode()).digest()[:6]
             encoded_hash = base64.urlsafe_b64encode(hash).decode()
-            return name, encoded_hash
-        pipfile = self.pipfile_location
-        clean_name, encoded_hash = get_name(name, pipfile)
+            return name, encoded_hash[:8]
+
+        clean_name, encoded_hash = get_name(name, self.pipfile_location)
         venv_name = '{0}-{1}'.format(clean_name, encoded_hash)
-        # Check for different capitalization of the same project on windows
-        if os.name == 'nt' and not PIPENV_VENV_IN_PROJECT and not self._get_virtualenv_location(venv_name):
-            from pipenv.patched.pew.pew import lsenvs
-            env_name = first([env for env in lsenvs() if env.lower().startswith(name.lower())])
-            if env_name:
-                env_name = env_name[:-9]
-                pipfile = self.pipfile_location.replace(name, env_name)
-                clean_name, encoded_hash = get_name(env_name, pipfile)
+
+        # This should work most of the time, for non-WIndows, in-project venv,
+        # or "proper" path casing (on Windows).
+        if (os.name != 'nt' or
+                PIPENV_VENV_IN_PROJECT or
+                self._get_virtualenv_location(venv_name)):
+            return clean_name, encoded_hash
+
+        # Check for different capitalization of the same project.
+        from pipenv.patched.pew.pew import lsenvs
+        for env in lsenvs():
+            env_name = env[:-9]
+            if not (env[-9] != '-' and
+                    env[-8:].isalpha() and
+                    env_name.lower() != name.lower()):
+                continue
+            return get_name(env_name, self.pipfile_location.replace(name, env_name))
+
+        # Use the default if no matching env exists.
         return clean_name, encoded_hash
 
+
     @property
     def virtualenv_name(self):
         sanitized, encoded_hash = self._get_virtualenv_hash(self.name)
@@ -326,7 +349,7 @@ class Project(object):
                 loc = pipfile.Pipfile.find(max_depth=PIPENV_MAX_DEPTH)
             except RuntimeError:
                 loc = None
-            self._pipfile_location = normalize_drive(loc)
+            self._pipfile_location = _normalized(loc)
         return self._pipfile_location
 
     @property