Implement %u format specifier

New test function for the new SubredditPage._url_str() function added to
test_subreddit.py. Being able to see the information this specifier adds
makes it trivial to tell if a post is a Reddit crosspost from a
SubredditPage (more trivial than manually parsing a full URL from %U,
anyway).

tests/test_subreddit.py

@@ -679,6 +679,24 @@ def test_subreddit_page__submission_attr(config, terminal, subreddit_page):
     terminal.attr.assert_called_with('SubmissionTitleSeen')
 
 
+def test_subreddit_page__url_str(config, terminal, subreddit_page):
+    data = {
+            'url_type': 'selfpost',
+            'url': 'self.AskReddit',
+            'url_full': 'https://www.reddit.com/r/AskReddit/comments/99eh6b/without_saying_what_the_category_is_what_are_your/'
+    }
+
+    assert subreddit_page._url_str(data) == 'self.AskReddit'
+
+    data['url_type'] = 'x-post subreddit'
+
+    assert subreddit_page._url_str(data) == 'self.AskReddit'
+
+    data['url_type'] = 'external'
+
+    assert subreddit_page._url_str(data) == 'https://www.reddit.com/r/AskReddit/comments/99eh6b/without_saying_what_the_category_is_what_are_your/'
+
+
 def test_subreddit_page__url_attr(config, terminal, subreddit_page):
     data = {}
     data['url_full'] = 'www.test.com'

tuir/subreddit_page.py

@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 
 import re
 import time
+from urllib.parse import urlparse
 
 from . import docs
 from .content import SubredditContent
@@ -251,6 +252,15 @@ class SubredditPage(Page):
         else:
             return self.term.attr('SubmissionTitle')
 
+    def _url_str(self, data):
+        # Both of these url_types indicate a URL of a subreddit/comment, and
+        # self.subreddit should be used as the display url
+        if data['url_type'] == 'selfpost' or \
+                data['url_type'].startswith('x-post'):
+            return data['url']
+        else:
+            return urlparse(data['url']).hostname
+
     def _url_attr(self, data):
         if data['url_full'] in self.config.history:
             return self.term.attr('LinkSeen')
@@ -331,7 +341,8 @@ class SubredditPage(Page):
                     lambda data: self.term.attr('SubmissionSubreddit'),
                     first))
             elif item == "%u":
-                raise NotImplementedError("'%u' subreddit_format specifier not yet supported")
+                form.append((lambda data: self._url_str(data),
+                    lambda data: self._url_attr(data), first))
             elif item == "%U":
                 form.append((lambda data: data['url'],
                     lambda data: self._url_attr(data), first))

tuir/templates/tuir.cfg

@@ -84,7 +84,7 @@ hide_username = False
 ; %E absolute edit time (NotImplemented)
 ; %a author
 ; %S subreddit
-; %u short url - 'self.reddit' or 'gfycat.com' (NotImplemented)
+; %u short url - 'self.reddit' or 'gfycat.com' for example
 ; %U full url
 ; %A saved
 ; %h hidden