Read git's yes/no and on/off booleans in get_value

git accepts yes/no and on/off for a boolean as well as true/false
(git_parse_maybe_bool_text in parse.c), and ConfigParser.getboolean on this
class already accepted all of them. _string_to_value handled only true/false,
under a comment claiming to "try boolean values as git uses them", so the two
accessors disagreed about the same file:

    value   get_value()   getboolean()   git config --type=bool
    yes     'yes'         True           true
    no      'no'          False          false
    on      'on'          True           true
    off     'off'         False          false

Returning them as strings was worse than merely inexact. "no" and "off" are
non-empty, so a caller testing the result of get_value got True for a value
git reads as false — the inversion is silent, since nothing raises.

_string_to_value now recognises the same spellings getboolean does. A value
that is not a boolean is untouched, so "meld" is still returned as a string,
and numeric values keep their existing behavior.

Not changed here: get_value also diverges on numeric bases and suffixes
("0x10" and "1k" come back as strings, "010" as 10 where git reads octal 8).
Those change the value rather than its type and are worth their own commit.

Validation: test_get_value_reads_git_boolean_spellings covers the ten
spellings and asserts the two accessors agree; it fails on the previous
revision. test/test_config.py passes (40 passed, 2 skipped), ruff check and
ruff format are clean. test/test_repo.py errors on this clone because
init-tests-after-clone.sh has not been run, unchanged by this commit.

Author: rawsun007

git/config.py

@@ -956,11 +956,16 @@ def _string_to_value(self, valuestr: str) -> Union[int, float, str, bool]:
                 continue
         # END for each numeric type
 
-        # Try boolean values as git uses them.
+        # Try boolean values as git uses them. git accepts yes/no and on/off as
+        # well as true/false (git_parse_maybe_bool_text in parse.c), and so does
+        # ConfigParser.getboolean on this class, so only get_value lagged behind.
+        # Leaving them as strings was worse than merely inexact: "no" and "off"
+        # are non-empty, so a caller testing the result got True for a value git
+        # reads as false.
         vl = valuestr.lower()
-        if vl == "false":
+        if vl in ("false", "no", "off"):
             return False
-        if vl == "true":
+        if vl in ("true", "yes", "on"):
             return True
 
         if not isinstance(valuestr, str):

test/test_config.py

@@ -167,6 +167,38 @@ def test_backslash_line_continuation(self):
             key = "co" if section == "alias" else "k"
             self.assertEqual(config.get_value(section, key), expected)
 
+    def test_get_value_reads_git_boolean_spellings(self):
+        # git accepts yes/no and on/off as well as true/false, and getboolean on
+        # this class already did. get_value returned them as strings, so "no" and
+        # "off" arrived as non-empty (truthy) values for a caller testing them.
+        cases = [
+            (b"true", True),
+            (b"TRUE", True),
+            (b"yes", True),
+            (b"Yes", True),
+            (b"on", True),
+            (b"On", True),
+            (b"false", False),
+            (b"no", False),
+            (b"off", False),
+            (b"Off", False),
+        ]
+        for raw, expected in cases:
+            config_file = io.BytesIO(b"[core]\n\tflag = " + raw + b"\n")
+            config_file.name = "boolean_spellings.config"
+            config = GitConfigParser(config_file)
+            config.read()
+            self.assertIs(config.get_value("core", "flag"), expected, raw.decode())
+            # The two accessors must not disagree about the same value.
+            self.assertIs(config.getboolean("core", "flag"), expected, raw.decode())
+
+        # A value that is not a boolean at all still comes back untouched.
+        config_file = io.BytesIO(b"[core]\n\tflag = meld\n")
+        config_file.name = "boolean_spellings.config"
+        config = GitConfigParser(config_file)
+        config.read()
+        self.assertEqual(config.get_value("core", "flag"), "meld")
+
     @with_rw_directory
     def test_comment_backslash_does_not_continue_value(self, rw_dir):
         config_path = osp.join(rw_dir, "config")