Consolidate and extract timestamp display functions in one file

The functionality for absolute timestamps was duplicated. A
function for displaying relative timestamps will be needed in
the next commit.

src/commands.rs

@@ -22,12 +22,11 @@ use std::sync::Mutex;
 use std::time::Instant;
 use std::{fs, io};
 
-use chrono::{FixedOffset, LocalResult, TimeZone, Utc};
 use clap::builder::NonEmptyStringValueParser;
 use clap::{ArgGroup, ArgMatches, CommandFactory, FromArgMatches, Subcommand};
 use config::Source;
 use itertools::Itertools;
-use jujutsu_lib::backend::{CommitId, ObjectId, Timestamp, TreeValue};
+use jujutsu_lib::backend::{CommitId, ObjectId, TreeValue};
 use jujutsu_lib::commit::Commit;
 use jujutsu_lib::dag_walk::topo_order_reverse;
 use jujutsu_lib::git::{GitFetchError, GitRefUpdate};
@@ -61,7 +60,7 @@ use crate::diff_util::{self, DiffFormat, DiffFormatArgs};
 use crate::formatter::{Formatter, PlainTextFormatter};
 use crate::graphlog::{AsciiGraphDrawer, Edge};
 use crate::progress::Progress;
-use crate::template_parser::TemplateParser;
+use crate::template_parser::{format_absolute_timestamp, TemplateParser};
 use crate::templater::Template;
 use crate::ui::Ui;
 
@@ -3343,26 +3342,6 @@ fn cmd_debug(
     Ok(())
 }
 
-// TODO: Move this somewhere where it can be reused by
-// `template_parser::SignatureTimestamp`.
-fn format_timestamp(timestamp: &Timestamp) -> String {
-    let utc = match Utc.timestamp_opt(
-        timestamp.timestamp.0.div_euclid(1000),
-        (timestamp.timestamp.0.rem_euclid(1000)) as u32 * 1000000,
-    ) {
-        LocalResult::None => {
-            return "<out-of-range date>".to_string();
-        }
-        LocalResult::Single(x) => x,
-        LocalResult::Ambiguous(y, _z) => y,
-    };
-    let datetime = utc.with_timezone(
-        &FixedOffset::east_opt(timestamp.tz_offset * 60)
-            .unwrap_or_else(|| FixedOffset::east_opt(0).unwrap()),
-    );
-    datetime.format("%Y-%m-%d %H:%M:%S.%3f %:z").to_string()
-}
-
 fn cmd_op_log(
     ui: &mut Ui,
     command: &CommandHelper,
@@ -3389,8 +3368,8 @@ fn cmd_op_log(
             formatter.with_label("time", |formatter| {
                 formatter.write_str(&format!(
                     "{} - {}",
-                    format_timestamp(&metadata.start_time),
+                    format_absolute_timestamp(&metadata.start_time),
-                    format_timestamp(&metadata.end_time)
+                    format_absolute_timestamp(&metadata.end_time)
                 ))
             })?;
             formatter.write_str("\n")?;

src/template_parser.rs

@@ -95,6 +95,7 @@ impl TemplateProperty<Signature, String> for SignatureEmail {
     }
 }
 
+// TODO: Find a better place for the timestamp functions, e.g. their own module
 fn datetime_from_timestamp(context: &Timestamp) -> Option<DateTime<FixedOffset>> {
     let utc = match Utc.timestamp_opt(
         context.timestamp.0.div_euclid(1000),
@@ -115,11 +116,15 @@ fn datetime_from_timestamp(context: &Timestamp) -> Option<DateTime<FixedOffset>>
     )
 }
 
-struct RelativeTimestampString;
+pub fn format_absolute_timestamp(timestamp: &Timestamp) -> String {
+    match datetime_from_timestamp(timestamp) {
+        Some(datetime) => datetime.format("%Y-%m-%d %H:%M:%S.%3f %:z").to_string(),
+        None => "<out-of-range date>".to_string(),
+    }
+}
 
-impl TemplateProperty<Timestamp, String> for RelativeTimestampString {
+pub fn format_timestamp_relative_to_now(timestamp: &Timestamp) -> String {
-    fn extract(&self, context: &Timestamp) -> String {
+    datetime_from_timestamp(timestamp)
-        datetime_from_timestamp(context)
         .and_then(|datetime| {
             let now = chrono::Local::now();
 
@@ -130,6 +135,13 @@ impl TemplateProperty<Timestamp, String> for RelativeTimestampString {
             f.convert(duration)
         })
         .unwrap_or_else(|| "<out-of-range date>".to_string())
+}
+
+struct RelativeTimestampString;
+
+impl TemplateProperty<Timestamp, String> for RelativeTimestampString {
+    fn extract(&self, context: &Timestamp) -> String {
+        format_timestamp_relative_to_now(context)
     }
 }
 
@@ -324,10 +336,7 @@ fn coerce_to_string<'a, I: 'a>(
         )),
         Property::Timestamp(property) => Box::new(TemplateFunction::new(
             property,
-            Box::new(|timestamp| match datetime_from_timestamp(&timestamp) {
+            Box::new(|timestamp| format_absolute_timestamp(&timestamp)),
-                Some(datetime) => datetime.format("%Y-%m-%d %H:%M:%S.%3f %:z").to_string(),
-                None => "<out-of-range date>".to_string(),
-            }),
         )),
     }
 }