Add a relative format similar to git graph (#103)

git log --graph has a format which tells me how long time ago a change
was made. it makes it a little bit easy to look for changes.

e.g. `git log --graph --abbrev-commit --decorate --format=format:'(%ar)'
--all`

Co-authored-by: Alexander Kjeldsen <alkk@danskespil.dk>

Author: drspx

docs/manual.md

@@ -192,10 +192,12 @@ Formatting strings use a subset of the placeholders available in `git log --form
 | %ae         | author email                                |
 | %ad         | author date                                 |
 | %as         | author date in short format `YYYY-MM-DD`    |
+| %ar         | author date, relative format (e.g., "21 hours ago") |
 | %cn         | committer name                              |
 | %ce         | committer email                             |
 | %cd         | committer date                              |
 | %cs         | committer date in short format `YYYY-MM-DD` |
+| %cr         | committer date, relative format (e.g., "4 days ago") |
 
 If you add a '+' (plus sign) after % of a placeholder, a line-feed is inserted immediately before the expansion if and only if the placeholder expands to a non-empty string.
 

src/print/format.rs

@@ -43,12 +43,14 @@ const AUTHOR: usize = 7;
 const AUTHOR_EMAIL: usize = 8;
 const AUTHOR_DATE: usize = 9;
 const AUTHOR_DATE_SHORT: usize = 10;
-const COMMITTER: usize = 11;
-const COMMITTER_EMAIL: usize = 12;
-const COMMITTER_DATE: usize = 13;
-const COMMITTER_DATE_SHORT: usize = 14;
-const BODY: usize = 15;
-const BODY_RAW: usize = 16;
+const AUTHOR_DATE_RELATIVE: usize = 11;
+const COMMITTER: usize = 12;
+const COMMITTER_EMAIL: usize = 13;
+const COMMITTER_DATE: usize = 14;
+const COMMITTER_DATE_SHORT: usize = 15;
+const COMMITTER_DATE_RELATIVE: usize = 16;
+const BODY: usize = 17;
+const BODY_RAW: usize = 18;
 
 const MODE_SPACE: usize = 1;
 const MODE_PLUS: usize = 2;
@@ -57,8 +59,8 @@ const MODE_MINUS: usize = 3;
 lazy_static! {
     pub static ref PLACEHOLDERS: Vec<[String; 4]> = {
         let base = vec![
-            "n", "H", "h", "P", "p", "d", "s", "an", "ae", "ad", "as", "cn", "ce", "cd", "cs", "b",
-            "B",
+            "n", "H", "h", "P", "p", "d", "s", "an", "ae", "ad", "as", "ar", "cn", "ce", "cd",
+            "cs", "cr", "b", "B",
         ];
         base.iter()
             .map(|b| {
@@ -260,6 +262,14 @@ pub fn format_commit(
                         }
                         write!(out, "{}", format_date(commit.author().when(), "%F"))
                     }
+                    AUTHOR_DATE_RELATIVE => {
+                        match mode {
+                            MODE_SPACE => write!(out, " ").unwrap(),
+                            MODE_PLUS => add_line(&mut lines, &mut out, wrapping),
+                            _ => {}
+                        }
+                        write!(out, "{}", format_relative_time(commit.author().when()))
+                    }
                     COMMITTER => {
                         match mode {
                             MODE_SPACE => write!(out, " ").unwrap(),
@@ -296,6 +306,14 @@ pub fn format_commit(
                         }
                         write!(out, "{}", format_date(commit.committer().when(), "%F"))
                     }
+                    COMMITTER_DATE_RELATIVE => {
+                        match mode {
+                            MODE_SPACE => write!(out, " ").unwrap(),
+                            MODE_PLUS => add_line(&mut lines, &mut out, wrapping),
+                            _ => {}
+                        }
+                        write!(out, "{}", format_relative_time(commit.committer().when()))
+                    }
                     BODY => {
                         let message = commit
                             .message()
@@ -517,6 +535,38 @@ pub fn format_date(time: Time, format: &str) -> String {
     format!("{}", date.format(format))
 }
 
+/// Format a time as a relative time string (e.g., "21 hours ago", "4 days ago")
+pub fn format_relative_time(time: Time) -> String {
+    let commit_time =
+        Local::from_offset(&FixedOffset::east(time.offset_minutes())).timestamp(time.seconds(), 0);
+    let now = Local::now();
+    let duration = now.signed_duration_since(commit_time);
+
+    let seconds = duration.num_seconds();
+    let minutes = duration.num_minutes();
+    let hours = duration.num_hours();
+    let days = duration.num_hours() / 24;
+    let weeks = days / 7;
+    let months = days / 30;
+    let years = days / 365;
+
+    if seconds < 60 {
+        format!("{} seconds ago", seconds)
+    } else if minutes < 60 {
+        format!("{} minutes ago", minutes)
+    } else if hours < 24 {
+        format!("{} hours ago", hours)
+    } else if days < 7 {
+        format!("{} days ago", days)
+    } else if weeks < 4 {
+        format!("{} weeks ago", weeks)
+    } else if months < 12 {
+        format!("{} months ago", months)
+    } else {
+        format!("{} years ago", years)
+    }
+}
+
 fn append_wrapped(vec: &mut Vec<String>, str: String, wrapping: &Option<Options>) {
     if str.is_empty() {
         vec.push(str);