Add unit tests for all supported date formats including compact ISO8601 variants

Co-authored-by: Byron <63622+Byron@users.noreply.github.com>

Author: Copilot

gix-date/tests/time/parse.rs

@@ -339,6 +339,227 @@ mod relative {
     }
 }
 
+/// Tests for compact ISO8601 formats (YYYYMMDDTHHMMSS variants)
+/// These formats are parsed by gix-date but may not be universally
+/// supported across all Git versions, so they have dedicated unit tests
+/// rather than baseline tests.
+mod compact_iso8601 {
+    use gix_date::Time;
+
+    #[test]
+    fn full_format() {
+        // 20080214T203045 = Feb 14, 2008 20:30:45 UTC
+        assert_eq!(
+            gix_date::parse("20080214T203045", None).unwrap(),
+            Time {
+                seconds: 1203021045,
+                offset: 0,
+            },
+        );
+    }
+
+    #[test]
+    fn with_colons_in_time() {
+        // 20080214T20:30:45 = Feb 14, 2008 20:30:45 UTC
+        assert_eq!(
+            gix_date::parse("20080214T20:30:45", None).unwrap(),
+            Time {
+                seconds: 1203021045,
+                offset: 0,
+            },
+        );
+    }
+
+    #[test]
+    fn hour_minute_only() {
+        // 20080214T2030 = Feb 14, 2008 20:30:00 UTC
+        assert_eq!(
+            gix_date::parse("20080214T2030", None).unwrap(),
+            Time {
+                seconds: 1203021000,
+                offset: 0,
+            },
+        );
+    }
+
+    #[test]
+    fn hour_minute_with_colon() {
+        // 20080214T20:30 = Feb 14, 2008 20:30:00 UTC
+        assert_eq!(
+            gix_date::parse("20080214T20:30", None).unwrap(),
+            Time {
+                seconds: 1203021000,
+                offset: 0,
+            },
+        );
+    }
+
+    #[test]
+    fn hour_only() {
+        // 20080214T20 = Feb 14, 2008 20:00:00 UTC
+        assert_eq!(
+            gix_date::parse("20080214T20", None).unwrap(),
+            Time {
+                seconds: 1203019200,
+                offset: 0,
+            },
+        );
+    }
+
+    #[test]
+    fn with_timezone() {
+        // 20080214T203045-04:00 = Feb 14, 2008 20:30:45 -04:00
+        // UTC seconds = local time + 4 hours = 1203021045 + 14400 = 1203035445
+        assert_eq!(
+            gix_date::parse("20080214T203045-04:00", None).unwrap(),
+            Time {
+                seconds: 1203035445,
+                offset: -14400,
+            },
+        );
+    }
+
+    #[test]
+    fn with_space_before_timezone() {
+        // 20080214T203045 -04:00 = Feb 14, 2008 20:30:45 -04:00
+        // UTC seconds = local time + 4 hours = 1203021045 + 14400 = 1203035445
+        assert_eq!(
+            gix_date::parse("20080214T203045 -04:00", None).unwrap(),
+            Time {
+                seconds: 1203035445,
+                offset: -14400,
+            },
+        );
+    }
+
+    #[test]
+    fn with_subseconds_ignored() {
+        // Subsecond precision is ignored, like Git does
+        // 20080214T203045.019-04:00 = Feb 14, 2008 20:30:45.019 -04:00
+        // UTC seconds = local time + 4 hours = 1203021045 + 14400 = 1203035445
+        assert_eq!(
+            gix_date::parse("20080214T203045.019-04:00", None).unwrap(),
+            Time {
+                seconds: 1203035445,
+                offset: -14400,
+            },
+        );
+    }
+
+    #[test]
+    fn with_subseconds_no_timezone() {
+        // 20080214T000000.20 = Feb 14, 2008 00:00:00.20 UTC
+        assert_eq!(
+            gix_date::parse("20080214T000000.20", None).unwrap(),
+            Time {
+                seconds: 1202947200,
+                offset: 0,
+            },
+        );
+    }
+
+    #[test]
+    fn with_subseconds_colon_time() {
+        // 20080214T00:00:00.20 = Feb 14, 2008 00:00:00.20 UTC
+        assert_eq!(
+            gix_date::parse("20080214T00:00:00.20", None).unwrap(),
+            Time {
+                seconds: 1202947200,
+                offset: 0,
+            },
+        );
+    }
+}
+
+/// Tests for ISO8601 with dots format (YYYY.MM.DD HH:MM:SS offset)
+mod iso8601_dots {
+    use gix_date::Time;
+
+    #[test]
+    fn basic() {
+        // 2008.02.14 20:30:45 -0500
+        // UTC seconds = local time + 5 hours = 1203021045 + 18000 = 1203039045
+        assert_eq!(
+            gix_date::parse("2008.02.14 20:30:45 -0500", None).unwrap(),
+            Time {
+                seconds: 1203039045,
+                offset: -18000,
+            },
+        );
+    }
+}
+
+/// Tests for flexible timezone offset formats
+mod flexible_offset {
+    use gix_date::Time;
+
+    #[test]
+    fn z_suffix_for_utc() {
+        // 1970-01-01 00:00:00 Z = Unix epoch
+        assert_eq!(
+            gix_date::parse("1970-01-01 00:00:00 Z", None).unwrap(),
+            Time { seconds: 0, offset: 0 },
+        );
+    }
+
+    #[test]
+    fn two_digit_hour_offset() {
+        // 2008-02-14 20:30:45 -05 = 2008-02-14 20:30:45 -0500
+        // UTC seconds = local time + 5 hours = 1203021045 + 18000 = 1203039045
+        assert_eq!(
+            gix_date::parse("2008-02-14 20:30:45 -05", None).unwrap(),
+            Time {
+                seconds: 1203039045,
+                offset: -18000,
+            },
+        );
+    }
+
+    #[test]
+    fn colon_separated_offset() {
+        // 2008-02-14 20:30:45 -05:00 = 2008-02-14 20:30:45 -0500
+        // UTC seconds = local time + 5 hours = 1203021045 + 18000 = 1203039045
+        assert_eq!(
+            gix_date::parse("2008-02-14 20:30:45 -05:00", None).unwrap(),
+            Time {
+                seconds: 1203039045,
+                offset: -18000,
+            },
+        );
+    }
+
+    #[test]
+    fn fifteen_minute_offset() {
+        // 2008-02-14 20:30:45 -0015
+        // UTC seconds = local time + 15 min = 1203021045 + 900 = 1203021945
+        assert_eq!(
+            gix_date::parse("2008-02-14 20:30:45 -0015", None).unwrap(),
+            Time {
+                seconds: 1203021945,
+                offset: -900,
+            },
+        );
+    }
+}
+
+/// Tests for subsecond precision in ISO8601 formats (ignored like Git)
+mod subsecond_precision {
+    use gix_date::Time;
+
+    #[test]
+    fn iso8601_with_subseconds() {
+        // 2008-02-14 20:30:45.019-04:00 - subseconds ignored
+        // UTC seconds = local time + 4 hours = 1203021045 + 14400 = 1203035445
+        assert_eq!(
+            gix_date::parse("2008-02-14 20:30:45.019-04:00", None).unwrap(),
+            Time {
+                seconds: 1203035445,
+                offset: -14400,
+            },
+        );
+    }
+}
+
 /// Various cases the fuzzer found
 mod fuzz {
     #[test]