feat: Format git-style RFC 2822 date strings

Git outputs the day-of-month field as a non-padded number whereas strict
RFC 2822 date strings are supposed to use a zero-padded two-digit number.

The new git_date::time::format::GIT_RFC2822 format description allows Time
to be formatted in git's RFC 2822 style. (Whereas the existing RFC2822
format description produces a strict RFC 2822 date string).

Refs: #679

Signed-off-by: Peter Grayson <pete@jpgrayson.net>

git-date/src/time/format.rs

@@ -10,6 +10,16 @@ pub const RFC2822: &[FormatItem<'_>] = format_description!(
     "[weekday repr:short], [day] [month repr:short] [year] [hour]:[minute]:[second] [offset_hour sign:mandatory][offset_minute]"
 );
 
+/// E.g. `Thu, 8 Aug 2022 12:45:06 +0800`. This is output by `git log --pretty=%aD`.
+pub const GIT_RFC2822: &[FormatItem<'_>] = format_description!(
+    "[weekday repr:short], \
+     [day padding:none] \
+     [month repr:short] \
+     [year] \
+     [hour]:[minute]:[second] \
+     [offset_hour sign:mandatory][offset_minute]"
+);
+
 /// E.g. `2022-08-17 22:04:58 +0200`
 pub const ISO8601: &[FormatItem<'_>] =
     format_description!("[year]-[month]-[day] [hour]:[minute]:[second] [offset_hour sign:mandatory][offset_minute]");

git-date/tests/time/format.rs

@@ -39,6 +39,15 @@ fn rfc2822() {
     assert_eq!(time_dec1().format(format::RFC2822), "Sat, 01 Dec 1973 00:03:09 +0230");
 }
 
+#[test]
+fn git_rfc2822() {
+    assert_eq!(time().format(format::GIT_RFC2822), "Fri, 30 Nov 1973 00:03:09 +0230");
+    assert_eq!(
+        time_dec1().format(format::GIT_RFC2822),
+        "Sat, 1 Dec 1973 00:03:09 +0230"
+    );
+}
+
 #[test]
 fn default() {
     assert_eq!(