template: add contained_in method to commit object in templates

this allows to conditionally display or label elements depending on 
whether the given commit is contained within the revset

CHANGELOG.md

@@ -65,6 +65,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * `jj rebase -r` now accepts `--insert-after` and `--insert-before` options to
   customize the location of the rebased revisions.
 
+* Commit objects in templates now have a `containted_in(revset: String) -> Boolean` method.
+
 ### Fixed bugs
 
 * Revsets now support `\`-escapes in string literal.

cli/src/commit_templater.rs

@@ -27,7 +27,7 @@ use jj_lib::id_prefix::IdPrefixContext;
 use jj_lib::object_id::ObjectId as _;
 use jj_lib::op_store::{RefTarget, WorkspaceId};
 use jj_lib::repo::Repo;
-use jj_lib::revset::{Revset, RevsetParseContext};
+use jj_lib::revset::{self, Revset, RevsetExpression, RevsetParseContext};
 use jj_lib::{git, rewrite};
 use once_cell::unsync::OnceCell;
 
@@ -620,6 +620,20 @@ fn builtin_commit_methods<'repo>() -> CommitTemplateBuildMethodFnMap<'repo, Comm
             Ok(L::wrap_boolean(out_property))
         },
     );
+    map.insert(
+        "contained_in",
+        |language, _build_ctx, self_property, function| {
+            let [revset_node] = template_parser::expect_exact_arguments(function)?;
+
+            let is_contained =
+                template_parser::expect_string_literal_with(revset_node, |revset, span| {
+                    Ok(evaluate_user_revset(language, span, revset)?.containing_fn())
+                })?;
+
+            let out_property = self_property.map(move |commit| is_contained(commit.id()));
+            Ok(L::wrap_boolean(out_property))
+        },
+    );
     map.insert(
         "conflict",
         |_language, _build_ctx, self_property, function| {
@@ -666,27 +680,48 @@ fn extract_working_copies(repo: &dyn Repo, commit: &Commit) -> String {
 
 type RevsetContainingFn<'repo> = dyn Fn(&CommitId) -> bool + 'repo;
 
+fn evaluate_revset_expression<'repo>(
+    language: &CommitTemplateLanguage<'repo>,
+    span: pest::Span<'_>,
+    expression: Rc<RevsetExpression>,
+) -> Result<Box<dyn Revset + 'repo>, TemplateParseError> {
+    let symbol_resolver = revset_util::default_symbol_resolver(
+        language.repo,
+        language.revset_parse_context.extensions.symbol_resolvers(),
+        language.id_prefix_context,
+    );
+    let revset =
+        revset_util::evaluate(language.repo, &symbol_resolver, expression).map_err(|err| {
+            TemplateParseError::expression("Failed to evaluate revset", span).with_source(err)
+        })?;
+    Ok(revset)
+}
+
 fn evaluate_immutable_revset<'repo>(
     language: &CommitTemplateLanguage<'repo>,
     span: pest::Span<'_>,
 ) -> Result<Box<dyn Revset + 'repo>, TemplateParseError> {
-    let repo = language.repo;
     // Alternatively, a negated (i.e. visible mutable) set could be computed.
     // It's usually smaller than the immutable set. The revset engine can also
     // optimize "::<recent_heads>" query to use bitset-based implementation.
     let expression = revset_util::parse_immutable_expression(&language.revset_parse_context)
         .map_err(|err| {
             TemplateParseError::expression("Failed to parse revset", span).with_source(err)
         })?;
-    let symbol_resolver = revset_util::default_symbol_resolver(
-        repo,
-        language.revset_parse_context.extensions.symbol_resolvers(),
-        language.id_prefix_context,
-    );
-    let revset = revset_util::evaluate(repo, &symbol_resolver, expression).map_err(|err| {
-        TemplateParseError::expression("Failed to evaluate revset", span).with_source(err)
+
+    evaluate_revset_expression(language, span, expression)
+}
+
+fn evaluate_user_revset<'repo>(
+    language: &CommitTemplateLanguage<'repo>,
+    span: pest::Span<'_>,
+    revset: &str,
+) -> Result<Box<dyn Revset + 'repo>, TemplateParseError> {
+    let expression = revset::parse(revset, &language.revset_parse_context).map_err(|err| {
+        TemplateParseError::expression("Failed to parse revset", span).with_source(err)
     })?;
-    Ok(revset)
+
+    evaluate_revset_expression(language, span, expression)
 }
 
 /// Branch or tag name with metadata.

cli/tests/test_commit_template.rs

@@ -658,3 +658,101 @@ fn test_log_immutable() {
     2: Revision "unknown_symbol" doesn't exist
     "###);
 }
+
+#[test]
+fn test_log_contained_in() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+    test_env.jj_cmd_ok(&repo_path, &["new", "-mA", "root()"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "-mB"]);
+    test_env.jj_cmd_ok(&repo_path, &["branch", "create", "main"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "-mC"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "-mD", "root()"]);
+
+    let template_for_revset = |revset: &str| {
+        format!(
+            r#"
+    separate(" ",
+      description.first_line(),
+      branches,
+      if(self.contained_in("{revset}"), "[contained_in]"),
+    ) ++ "\n"
+    "#
+        )
+    };
+
+    let stdout = test_env.jj_cmd_success(
+        &repo_path,
+        &[
+            "log",
+            "-r::",
+            "-T",
+            &template_for_revset(r#"description(A)::"#),
+        ],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    @  D
+    │ ◉  C [contained_in]
+    │ ◉  B main [contained_in]
+    │ ◉  A [contained_in]
+    ├─╯
+    ◉
+    "###);
+
+    let stdout = test_env.jj_cmd_success(
+        &repo_path,
+        &[
+            "log",
+            "-r::",
+            "-T",
+            &template_for_revset(r#"visible_heads()"#),
+        ],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    @  D [contained_in]
+    │ ◉  C [contained_in]
+    │ ◉  B main
+    │ ◉  A
+    ├─╯
+    ◉
+    "###);
+
+    // Suppress error that could be detected earlier
+    let stderr = test_env.jj_cmd_failure(
+        &repo_path,
+        &["log", "-r::", "-T", &template_for_revset("unknown_fn()")],
+    );
+    insta::assert_snapshot!(stderr, @r###"
+    Error: Failed to parse template: Failed to parse revset
+    Caused by:
+    1:  --> 5:28
+      |
+    5 |       if(self.contained_in("unknown_fn()"), "[contained_in]"),
+      |                            ^------------^
+      |
+      = Failed to parse revset
+    2:  --> 1:1
+      |
+    1 | unknown_fn()
+      | ^--------^
+      |
+      = Function "unknown_fn" doesn't exist
+    "###);
+
+    let stderr = test_env.jj_cmd_failure(
+        &repo_path,
+        &["log", "-r::", "-T", &template_for_revset("unknown_symbol")],
+    );
+    insta::assert_snapshot!(stderr, @r###"
+    Error: Failed to parse template: Failed to evaluate revset
+    Caused by:
+    1:  --> 5:28
+      |
+    5 |       if(self.contained_in("unknown_symbol"), "[contained_in]"),
+      |                            ^--------------^
+      |
+      = Failed to evaluate revset
+    2: Revision "unknown_symbol" doesn't exist
+    "###);
+}

docs/templates.md

@@ -91,6 +91,7 @@ This type cannot be printed. The following methods are defined.
 * `hidden() -> Boolean`: True if the commit is not visible (a.k.a. abandoned).
 * `immutable() -> Boolean`: True if the commit is included in [the set of
   immutable commits](config.md#set-of-immutable-commits).
+* `contained_in(revset: String) -> Boolean`: True if the commit is included in [the provided revset](revsets.md).
 * `conflict() -> Boolean`: True if the commit contains merge conflicts.
 * `empty() -> Boolean`: True if the commit modifies no files.
 * `root() -> Boolean`: True if the commit is the root commit.