templater: display both name and email by author/committer keywords

This is an example of labeled output of structured value types. I think
"{name} <{email}>" is a good default formatting, but I should note that
the signature also contains timestamp field.

CHANGELOG.md

@@ -23,6 +23,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * `jj log` prefixes commit descriptions with "(empty)" when they contain no
   change compared to their parents.
 
+* The `author`/`committer` templates now display both name and email. Use
+  `author.name()`/`committer.name()` to extract the name.
+
 ### New features
 
 * The default log format now uses the committer timestamp instead of the author

src/commands/mod.rs

@@ -1233,8 +1233,8 @@ fn cmd_show(ui: &mut Ui, command: &CommandHelper, args: &ShowArgs) -> Result<(),
         r#"
             "Commit ID: " commit_id "\n"
             "Change ID: " change_id "\n"
-            "Author: " author " <" author.email() "> (" {author_timestamp_template} ")\n"
-            "Committer: " committer " <" committer.email() "> (" {committer_timestamp_template} ")\n"
+            "Author: " author " (" {author_timestamp_template} ")\n"
+            "Committer: " committer " (" {committer_timestamp_template} ")\n"
             "\n"
             description
             "\n""#,

src/templater.rs

@@ -33,7 +33,11 @@ pub trait Template<C> {
 
 impl Template<()> for Signature {
     fn format(&self, _: &(), formatter: &mut dyn Formatter) -> io::Result<()> {
-        formatter.write_str(&self.name)
+        write!(formatter, "{}", self.name)?;
+        write!(formatter, " <")?;
+        write!(formatter.labeled("email"), "{}", self.email)?;
+        write!(formatter, ">")?;
+        Ok(())
     }
 }