date: allow negative date offsets

Issue #7515
Clap needs to be specifically configured to allow values
with a leading hyphen.

src/uu/date/src/date.rs

@@ -318,6 +318,7 @@ pub fn uu_app() -> Command {
                 .short('d')
                 .long(OPT_DATE)
                 .value_name("STRING")
+                .allow_hyphen_values(true)
                 .help("display time described by STRING, not 'now'"),
         )
         .arg(

tests/by-util/test_date.rs

@@ -1,3 +1,4 @@
+use chrono::{DateTime, Duration, Utc};
 // This file is part of the uutils coreutils package.
 //
 // For the full copyright and license information, please view the LICENSE
@@ -410,6 +411,31 @@ fn test_date_string_human() {
     }
 }
 
+#[test]
+fn test_negative_offset() {
+    let data_formats = vec![
+        ("-1 hour", Duration::hours(1)),
+        ("-1 hours", Duration::hours(1)),
+        ("-1 day", Duration::days(1)),
+        ("-2 weeks", Duration::weeks(2)),
+    ];
+    for (date_format, offset) in data_formats {
+        new_ucmd!()
+            .arg("-d")
+            .arg(date_format)
+            .arg("--rfc-3339=seconds")
+            .succeeds()
+            .stdout_str_check(|out| {
+                let date = DateTime::parse_from_rfc3339(out.trim()).unwrap();
+
+                // Is the resulting date roughly what is expected?
+                let expected_date = Utc::now() - offset;
+                date > expected_date - Duration::minutes(10)
+                    && date < expected_date + Duration::minutes(10)
+            });
+    }
+}
+
 #[test]
 fn test_invalid_date_string() {
     new_ucmd!()