fix: format float timezone offsets as integer fields

`altz_to_utctz_str` accepts float seconds, but floor division preserves their float type. Formatting `19800.0` therefore emitted `-5.030.0` rather than Git's `-0530` offset.

Compute whole minutes as an integer and split them with `divmod`, preserving existing sign and sub-minute truncation behavior. Add six regressions covering zero, positive/negative offsets and fractional seconds. All six fail before the fix and pass afterward; applicable pre-commit checks pass.

Assisted-by: OpenAI Codex (model: unknown, autonomous)

Author: gavenren

git/objects/util.py

@@ -161,8 +161,7 @@ def altz_to_utctz_str(altz: float) -> str:
     :param altz:
         Timezone offset in seconds west of UTC.
     """
-    hours = abs(altz) // 3600
-    minutes = (abs(altz) % 3600) // 60
+    hours, minutes = divmod(int(abs(altz) // 60), 60)
     sign = "-" if altz >= 60 else "+"
     return "{}{:02}{:02}".format(sign, hours, minutes)
 

test/test_util.py

@@ -280,6 +280,17 @@ def __repr__(self):
         return f"{type(self).__name__}({self.name!r})"
 
 
+@pytest.mark.parametrize(
+    "offset, expected",
+    [(0.0, "+0000"), (19800.0, "-0530"), (-19800.0, "+0530"), (34200.9, "-0930"), (60.1, "-0001"), (-59.9, "+0000")],
+)
+def test_altz_to_utctz_str_accepts_float_seconds(offset, expected):
+    result = altz_to_utctz_str(offset)
+    assert result == expected
+    assert verify_utctz(result) == result
+    assert utctz_to_altz(result) == utctz_to_altz(expected)
+
+
 @ddt.ddt
 class TestUtils(TestBase):
     """Tests for most utilities in :mod:`git.util`."""