lint: Allow anchor tags to span up to four lines.

This starts to address 1533.  I still think the </p> tags
should be on their own line lined up with the start tag,
so the linter won't let through the specific example
shown in the ticket.

tools/lib/template_parser.py

@@ -153,13 +153,19 @@ def validate(fn=None, text=None, check_indent=True):
             end_line = end_token.line
             end_col = end_token.col
 
+            if start_tag == 'a':
+                max_lines = 3
+            else:
+                max_lines = 1
+
             problem = None
             if (start_tag == 'code') and (end_line == start_line + 1):
                 problem = 'Code tag is split across two lines.'
             if start_tag != end_tag:
                 problem = 'Mismatched tag.'
-            elif check_indent and end_line > start_line + 1 and end_col != start_col:
-                problem = 'Bad indentation.'
+            elif check_indent and (end_line > start_line + max_lines):
+                if end_col != start_col:
+                    problem = 'Bad indentation.'
             if problem:
                 raise Exception('''
                     fn: %s

tools/tests/test_template_parser.py

@@ -79,6 +79,31 @@ class ParserTest(unittest.TestCase):
         with self.assertRaisesRegexp(Exception, 'split across two lines'): # type: ignore
             validate(text=my_html)
 
+    def test_anchor_blocks(self):
+        # type: () -> None
+
+        # This is allowed, although strange.
+        my_html = '''
+            <a hef="/some/url">
+            Click here
+            for more info.
+            </a>'''
+        validate(text=my_html)
+
+        # This is fine.
+        my_html = '<a href="/some/url">click here</a>'
+        validate(text=my_html)
+
+        # Even this is fine.
+        my_html = '''
+            <a class="twitter-timeline" href="https://twitter.com/ZulipStatus"
+                data-widget-id="443457763394334720"
+                data-screen-name="ZulipStatus"
+                >@ZulipStatus on Twitter</a>.
+            '''
+        validate(text=my_html)
+
+
     def test_tokenize(self):
         # type: () -> None
         tag = '<meta whatever>bla'