Pip's name key can now accept remote package address.

Summary:

Pip module would abort when name is a remote package address because
the module was expecting a version if ``=`` is part of the name value.

Furthermore, the pip module would require either name or requirement to
be a key, although the documentation table said neither was required.
The fact that one of them must be present is not documented in the
documentation leads to confusion. This commit added this fact as part
of description.

In this commit, we resolve the confusion by stating either ``name``
or ``requirement`` is needed. Next, if the user puts remote address
as the value of the ``name`` key, we will not use mirror. Lastly,
if the user uses the remote serivice address as the name of the
package and the user does not supply -e option in extra_vars
(which is the whole point of this commit), we will add -e to
 extra_vars so pip command can run with -e option.

library/packaging/pip

@@ -26,12 +26,13 @@ DOCUMENTATION = '''
 module: pip
 short_description: Manages Python library dependencies.
 description:
-     - Manage Python library dependencies.
+     - Manage Python library dependencies. To use this module, one of the following keys is required: C(name)
+       or C(requirements).
 version_added: "0.7"
 options:
   name:
     description:
-      - The name of a Python library to install
+      - The name of a Python library to install or the url of the remote package. 
     required: false
     default: null
   version:
@@ -93,6 +94,8 @@ examples:
      description: Install I(flask) python package.
    - code: "pip: name=flask version=0.8"
      description: Install I(flask) python package on version 0.8.
+   - code: "pip: name='svn+http://myrepo/svn/MyApp#egg=MyApp'"
+     description: Install I(MyApp) using one of the remote protocols (bzr,hg,git,svn) C(pip) supports. You do not have to supply '-e' option in extra_args.
    - code: "pip: name=flask virtualenv=/my_app/venv"
      description: "Install I(Flask) (U(http://flask.pocoo.org/)) into the specified I(virtualenv), inheriting none of the globally installed modules"
    - code: "pip: name=flask virtualenv=/my_app/venv virtualenv_site_packages=yes"
@@ -180,6 +183,15 @@ def main():
 
     if state == 'latest' and version is not None:
         module.fail_json(msg='version is incompatible with state=latest')
+
+    # before we move on, check if name is #egg (remote repository/package)
+    # if it is, mark it as package so we can skip --use-mirrors and skip
+    # version arg checks
+    is_package = False
+    if '#egg=' in name:
+        is_package = True
+    else:
+        # we have to handle the case when version is required for non-remote package
         if name and '=' in name:
             module.fail_json(msg='version must be specified in the version parameter')
     
@@ -208,7 +220,19 @@ def main():
     pip = _get_pip(module, env)
 
     cmd = '%s %s' % (pip, state_map[state])
-    if state != 'absent' and use_mirrors:
+
+    # If is_package is True, we must not add --use-mirrors option.
+    # Also, if -e option is not added by the user via extra_args, 
+    # we must add -e ourselves. 
+    if is_package:
+        args_list = []  # used if extra_args is not used at all
+        if extra_args:
+            args_list = extra_args.split(' ')            
+        if '-e' not in args_list:
+            args_list.append('-e')
+            # Ok, we will reconstruct the option string
+            extra_args = ' '.join(args_list)
+    if not is_package or state != 'absent' and use_mirrors:
         cmd += ' --use-mirrors'
     if extra_args:
         cmd += ' %s' % extra_args