refactor

* use `gix_date::Time` instead of buffer-based time.

```
❯ ein t hours
 08:25:34 traverse commit graph done 1.3M commits in 9.12s (143.6K commits/s)
 08:25:34        estimate-hours Extracted and organized data from 1309152 commits in 7.67ms (170684736 commits/s)
total hours: 1243723.88
total 8h days: 155465.48
total commits = 1309152
total authors: 34641
total unique authors: 26510 (23.47% duplication)

linux ( master) +408 -798 [!⇣14583] took 9s

❯ /Users/byron/dev/github.com/GitoxideLabs/gitoxide/target/release/ein t hours
 08:26:42 traverse commit graph done 1.3M commits in 7.84s (167.1K commits/s)
 08:26:43        estimate-hours Extracted and organized data from 1309152 commits in 39.432084ms (33200174 commits/s)
total hours: 1243723.88
total 8h days: 155465.48
total commits = 1309152
total authors: 34641
total unique authors: 26510 (23.47% duplication)

linux ( master) +408 -798 [!⇣14583] took 8s

❯ /Users/byron/dev/github.com/GitoxideLabs/gitoxide/target/release/ein t hours
 08:32:59 traverse commit graph done 1.3M commits in 7.73s (169.4K commits/s)
 08:32:59        estimate-hours Extracted and organized data from 1309152 commits in 5.423541ms (241383248 commits/s)
total hours: 1243723.88
total 8h days: 155465.48
total commits = 1309152
total authors: 34641
total unique authors: 26510 (23.47% duplication)
```

Author: Byron

gitoxide-core/src/hours/core.rs

@@ -17,7 +17,7 @@ const MINUTES_PER_HOUR: f32 = 60.0;
 pub const HOURS_PER_WORKDAY: f32 = 8.0;
 
 pub fn estimate_hours(
-    commits: &[(u32, gix::actor::SignatureRef<'static>)],
+    commits: &[(u32, super::SignatureRef<'static>)],
     stats: &[(u32, FileStats, LineStats)],
 ) -> WorkByEmail {
     assert!(!commits.is_empty());

gitoxide-core/src/hours/mod.rs

@@ -2,7 +2,6 @@ use std::{collections::BTreeSet, io, path::Path, time::Instant};
 
 use anyhow::bail;
 use gix::{
-    actor,
     bstr::{BStr, ByteSlice},
     prelude::*,
     progress, Count, NestedProgress, Progress,
@@ -27,6 +26,18 @@ pub struct Context<W> {
     pub out: W,
 }
 
+pub struct SignatureRef<'a> {
+    name: &'a BStr,
+    email: &'a BStr,
+    time: gix_date::Time,
+}
+
+impl SignatureRef<'_> {
+    fn seconds(&self) -> gix_date::SecondsSinceUnixEpoch {
+        self.time.seconds
+    }
+}
+
 /// Estimate the hours it takes to produce the content of the repository in `_working_dir_`, with `_refname_` for
 /// the start of the commit graph traversal.
 ///
@@ -82,10 +93,15 @@ where
                         };
                         let name = string_ref(author.name.as_ref());
                         let email = string_ref(author.email.as_ref());
-                        let mut buf = Vec::with_capacity(64);
-                        let time = string_ref(author.time.to_ref(&mut buf));
 
-                        out.push((commit_idx, actor::SignatureRef { name, email, time }));
+                        out.push((
+                            commit_idx,
+                            SignatureRef {
+                                name,
+                                email,
+                                time: author.time,
+                            },
+                        ));
                     }
                 }
                 out.shrink_to_fit();