feat: Support git default date format

This is the format output by default by `git log` or when using
`--pretty=%ad`.

The new git_date::time::format::GIT_DEFAULT format description may be used
to output date strings in this format. It is also now used by
git_date::parse() to accept date strings that may be in this format.

Refs: #679

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

git-date/src/parse.rs

@@ -19,7 +19,7 @@ pub(crate) mod function {
     use crate::{
         parse::{relative, Error},
         time::{
-            format::{DEFAULT, ISO8601, ISO8601_STRICT, SHORT},
+            format::{DEFAULT, GIT_DEFAULT, ISO8601, ISO8601_STRICT, SHORT},
             Sign,
         },
         Time,
@@ -43,6 +43,8 @@ pub(crate) mod function {
             Time::new(val.unix_timestamp().try_into()?, val.offset().whole_seconds())
         } else if let Ok(val) = OffsetDateTime::parse(input, DEFAULT) {
             Time::new(val.unix_timestamp().try_into()?, val.offset().whole_seconds())
+        } else if let Ok(val) = OffsetDateTime::parse(input, GIT_DEFAULT) {
+            Time::new(val.unix_timestamp().try_into()?, val.offset().whole_seconds())
         } else if let Ok(val) = u32::from_str(input) {
             // Format::Unix
             Time::new(val, 0)

git-date/src/time/format.rs

@@ -39,6 +39,16 @@ pub const DEFAULT: &[FormatItem<'_>] = format_description!(
     "[weekday repr:short] [month repr:short] [day] [year] [hour]:[minute]:[second] [offset_hour sign:mandatory][offset_minute]"
 );
 
+/// E.g. `Thu Sep 4 10:45:06 2022 -0400`. This is output by `git log --pretty=%ad`.
+pub const GIT_DEFAULT: &[FormatItem<'_>] = format_description!(
+    "[weekday repr:short] \
+     [month repr:short] \
+     [day padding:none] \
+     [hour]:[minute]:[second] \
+     [year] \
+     [offset_hour sign:mandatory][offset_minute]"
+);
+
 mod format_impls {
     use time::format_description::FormatItem;
 

git-date/tests/time/format.rs

@@ -54,6 +54,22 @@ fn default() {
         time().format(git_date::time::format::DEFAULT),
         "Fri Nov 30 1973 00:03:09 +0230"
     );
+    assert_eq!(
+        time_dec1().format(git_date::time::format::DEFAULT),
+        "Sat Dec 01 1973 00:03:09 +0230"
+    )
+}
+
+#[test]
+fn git_default() {
+    assert_eq!(
+        time().format(git_date::time::format::GIT_DEFAULT),
+        "Fri Nov 30 00:03:09 1973 +0230"
+    );
+    assert_eq!(
+        time_dec1().format(git_date::time::format::GIT_DEFAULT),
+        "Sat Dec 1 00:03:09 1973 +0230"
+    )
 }
 
 #[test]

git-date/tests/time/parse.rs

@@ -82,6 +82,19 @@ fn raw() {
     );
 }
 
+#[test]
+fn git_default() {
+    assert_eq!(
+        git_date::parse("Thu Aug 8 12:45:06 2022 +0800", None).expect("parsed git default string"),
+        Time {
+            seconds_since_unix_epoch: 1659933906,
+            offset_in_seconds: 28800,
+            sign: Sign::Plus,
+        },
+        "could not parse with git default format"
+    );
+}
+
 #[test]
 fn invalid_dates_can_be_produced_without_current_time() {
     assert!(matches!(