templater: add shortest().prefix()/rest() accessors

This ensures that the "brackets" style can be emulated by a template
expression.

src/template_parser.rs

@@ -896,6 +896,20 @@ fn build_shortest_id_prefix_method<'a, I: 'a>(
     _build_keyword: &impl Fn(&str, pest::Span) -> TemplateParseResult<PropertyAndLabels<'a, I>>,
 ) -> TemplateParseResult<Property<'a, I>> {
     let property = match function.name {
+        "prefix" => {
+            expect_no_arguments(function)?;
+            Property::String(chain_properties(
+                self_property,
+                TemplatePropertyFn(|id: &ShortestIdPrefix| id.prefix.clone()),
+            ))
+        }
+        "rest" => {
+            expect_no_arguments(function)?;
+            Property::String(chain_properties(
+                self_property,
+                TemplatePropertyFn(|id: &ShortestIdPrefix| id.rest.clone()),
+            ))
+        }
         "with_brackets" => {
             // TODO: If we had a map function, this could be expressed as a template
             // like 'id.shortest() % (.prefix() if(.rest(), "[" .rest() "]"))'

src/templater.rs

@@ -609,8 +609,8 @@ impl Template<()> for CommitOrChangeId<'_> {
 }
 
 pub struct ShortestIdPrefix {
-    prefix: String,
-    rest: String,
+    pub prefix: String,
+    pub rest: String,
 }
 
 impl ShortestIdPrefix {

tests/test_log_command.rs

@@ -288,6 +288,18 @@ fn test_log_prefix_highlight_brackets() {
     let test_env = TestEnvironment::default();
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
+    let render = |rev, template| {
+        test_env.jj_cmd_success(
+            &repo_path,
+            &["log", "--no-graph", "-r", rev, "-T", template],
+        )
+    };
+    test_env.add_config(
+        r###"
+        [template-aliases]
+        'format_id(id)' = 'id.shortest(12).prefix() "[" id.shortest(12).rest() "]"'
+        "###,
+    );
 
     fn prefix_format(len: Option<usize>) -> String {
         format!(
@@ -377,6 +389,22 @@ fn test_log_prefix_highlight_brackets() {
     o  Change zzz  00
     "###
     );
+
+    insta::assert_snapshot!(
+        render(":@", r#"format_id(change_id) " " format_id(commit_id) "\n""#),
+        @r###"
+    wq[nwkozpkust] 03[f51310b83e]
+    km[kuslswpqwq] f7[7fb1909080]
+    kp[qxywonksrl] e7[15ad5db646]
+    zn[kkpsqqskkl] 38[622e54e2e5]
+    yo[stqsxwqrlt] 0cf[42f60199c]
+    vr[uxwmqvtpmx] 9e[6015e4e622]
+    yq[osqzytrlsw] 06f[34d9b1475]
+    ro[yxmykxtrkr] 1f[99a5e19891]
+    mz[vwutvlkqwt] 7b[1f7dee65b4]
+    qpv[untsmwlqt] ba1[a30916d29]
+    zzz[zzzzzzzzz] 00[0000000000]
+    "###);
 }
 
 #[test]