docs: reqfile options are now generated automatically

Author: Noah Gorny

docs/html/reference/pip_install.rst

@@ -156,18 +156,7 @@ To interpret the requirements file in UTF-8 format add a comment
 
 The following options are supported:
 
-  *  :ref:`-i, --index-url <install_--index-url>`
-  *  :ref:`--extra-index-url <install_--extra-index-url>`
-  *  :ref:`--no-index <install_--no-index>`
-  *  :ref:`-c, --constraint <install_--constraint>`
-  *  :ref:`-r, --requirement <install_--requirement>`
-  *  :ref:`-e, --editable <install_--editable>`
-  *  :ref:`-f, --find-links <install_--find-links>`
-  *  :ref:`--no-binary <install_--no-binary>`
-  *  :ref:`--only-binary <install_--only-binary>`
-  *  :ref:`--require-hashes <install_--require-hashes>`
-  *  :ref:`--pre <install_--pre>`
-  *  :ref:`--trusted-host <--trusted-host>`
+.. pip-reqfile-options-ref::
 
 For example, to specify :ref:`--no-index <install_--no-index>` and two
 :ref:`--find-links <install_--find-links>` locations:

docs/pip_sphinxext.py

@@ -10,6 +10,7 @@
 
 from pip._internal.cli import cmdoptions
 from pip._internal.commands import create_command
+from pip._internal.req.req_file import SUPPORTED_OPTIONS
 
 
 class PipCommandUsage(rst.Directive):
@@ -108,9 +109,40 @@ def process_options(self):
         )
 
 
+class PipReqFileOptionsReference(PipOptions):
+
+    def process_options(self):
+        for option in SUPPORTED_OPTIONS:
+            if getattr(option, 'deprecated', False):
+                continue
+
+            opt = option()
+            opt_name = opt._long_opts[0]
+            if opt._short_opts:
+                short_opt_name = '{}, '.format(opt._short_opts[0])
+            else:
+                short_opt_name = ''
+
+            from_install = (
+                'install_'
+                if option not in cmdoptions.general_group['options'] else
+                ''
+            )
+            self.view_list.append(
+                '  *  :ref:`{short}{long}<{prefix}{opt_name}>`'.format(
+                    short=short_opt_name,
+                    long=opt_name,
+                    prefix=from_install,
+                    opt_name=opt_name
+                ),
+                "\n"
+            )
+
+
 def setup(app):
     app.add_directive('pip-command-usage', PipCommandUsage)
     app.add_directive('pip-command-description', PipCommandDescription)
     app.add_directive('pip-command-options', PipCommandOptions)
     app.add_directive('pip-general-options', PipGeneralOptions)
     app.add_directive('pip-index-options', PipIndexOptions)
+    app.add_directive('pip-reqfile-options-ref', PipReqFileOptionsReference)