Add tests of ConfigParser with "..." with " or \ inside

These are cases where just removing the outer quotes without doing
anything to the text inside does not give the correct result, and
where keeping the quotes may be preferable, in that it was the
long-standing behavior of `GitConfigParser`.

That this was the long-standing behavior may justify bringing it
back when the `"`-`"`-enclosed text contains such characters, but
it does not justify preserving it indefinitely: it will still be
better to parse the escape sequences, at least in the type case
that all of them in a value's representation are well-formed.

test/fixtures/git_config_with_quotes_escapes

@@ -0,0 +1,9 @@
+[custom]
+  hasnewline = "first\nsecond"
+  hasbackslash = "foo\\bar"
+  hasquote = "ab\"cd"
+  hastrailingbackslash = "word\\"
+  hasunrecognized = "p\qrs"
+  hasunescapedquotes = "ab"cd"e"
+  ordinary = "hello world"
+  unquoted = good evening

test/test_config.py

@@ -428,6 +428,26 @@ def test_config_with_quotes_with_whitespace_outside_value(self):
         cr = GitConfigParser(fixture_path("git_config_with_quotes_whitespace_outside"), read_only=True)
         self.assertEqual(cr.get("init", "defaultBranch"), "trunk")
 
+    def test_config_with_quotes_containing_escapes(self):
+        """For now just suppress quote removal. But it would be good to interpret most of these."""
+        cr = GitConfigParser(fixture_path("git_config_with_quotes_escapes"), read_only=True)
+
+        # These can eventually be supported by substituting the represented character.
+        self.assertEqual(cr.get("custom", "hasnewline"), R'"first\nsecond"')
+        self.assertEqual(cr.get("custom", "hasbackslash"), R'"foo\\bar"')
+        self.assertEqual(cr.get("custom", "hasquote"), R'"ab\"cd"')
+        self.assertEqual(cr.get("custom", "hastrailingbackslash"), R'"word\\"')
+        self.assertEqual(cr.get("custom", "hasunrecognized"), R'"p\qrs"')
+
+        # It is less obvious whether and what to eventually do with this.
+        self.assertEqual(cr.get("custom", "hasunescapedquotes"), '"ab"cd"e"')
+
+        # Cases where quote removal is clearly safe should happen even after those.
+        self.assertEqual(cr.get("custom", "ordinary"), "hello world")
+
+        # Cases without quotes should still parse correctly even after those, too.
+        self.assertEqual(cr.get("custom", "unquoted"), "good evening")
+
     def test_get_values_works_without_requiring_any_other_calls_first(self):
         file_obj = self._to_memcache(fixture_path("git_config_multiple"))
         cr = GitConfigParser(file_obj, read_only=True)