Fixed issue #151 -- When running the install command, bail early if no requirement is given.

pip/commands/install.py

@@ -200,11 +200,18 @@ class InstallCommand(Command):
             for req in parse_requirements(filename, finder=finder, options=options):
                 requirement_set.add_requirement(req)
 
+        if not requirement_set.has_requirements:
+            if options.find_links:
+                raise InstallationError('You must give at least one '
+                    'requirement to %s (maybe you meant "pip install %s"?)'
+                    % (self.name, " ".join(options.find_links)))
+            raise InstallationError('You must give at least one '
+                'requirement to %s (see "pip help install")' % self.name)
+
         if (options.use_user_site and
             sys.version_info < (2, 6)):
-            
             raise InstallationError('--user is only supported in Python version 2.6 and newer')
-                
+
         import setuptools
         if (options.use_user_site and
             requirement_set.has_editables and

pip/req.py

@@ -774,6 +774,10 @@ class RequirementSet(object):
                 return True
         return False
 
+    @property
+    def has_requirements(self):
+        return self.requirements.values() or self.unnamed_requirements
+
     @property
     def has_editables(self):
         if any(req.editable for req in self.requirements.values()):

tests/test_proxy.py

@@ -15,7 +15,6 @@ import getpass
 from pip.basecommand import get_proxy
 from test_pip import here
 
-
 def new_getpass(prompt, answer='passwd'):
     print '%s%s' % (prompt, answer)
     return answer