Refactor away VcsSupport.get_backend_from_location().

src/pip/_internal/operations/freeze.py

@@ -173,12 +173,18 @@ class FrozenRequirement(object):
         """
         location = os.path.normcase(os.path.abspath(dist.location))
         from pip._internal.vcs import vcs, get_src_requirement
-        if not dist_is_editable(dist) or not vcs.get_backend_name(location):
+        if not dist_is_editable(dist):
+            req = dist.as_requirement()
+            return (req, False, [])
+
+        vc_name = vcs.get_backend_name(location)
+
+        if not vc_name:
             req = dist.as_requirement()
             return (req, False, [])
 
         try:
-            req = get_src_requirement(dist, location)
+            req = get_src_requirement(vc_name, dist, location)
         except InstallationError as exc:
             logger.warning(
                 "Error when trying to get requirement for VCS system %s, "

src/pip/_internal/vcs/__init__.py

@@ -150,12 +150,6 @@ class VcsSupport(object):
         if name in self._registry:
             return self._registry[name]
 
-    def get_backend_from_location(self, location):
-        vc_type = self.get_backend_name(location)
-        if vc_type:
-            return self.get_backend(vc_type)
-        return None
-
 
 vcs = VcsSupport()
 
@@ -487,8 +481,8 @@ class VersionControl(object):
         return cls.is_repository_directory(location)
 
 
-def get_src_requirement(dist, location):
+def get_src_requirement(vc_name, dist, location):
-    version_control = vcs.get_backend_from_location(location)
+    version_control = vcs.get_backend(vc_name)
     if version_control:
         try:
             return version_control().get_src_requirement(dist,