templater: make "git_head" return boolean, render it as "git_head()"

For the same reason as the root revision is indicated by "root()".

CHANGELOG.md

@@ -16,7 +16,8 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 * Evaluation error of `revsets.short-prefixes` configuration is now reported.
 
 * The `HEAD@git` symbol no longer resolves to the Git HEAD revision. Use
- `git_head()` or `@-` revset expression instead.
+ `git_head()` or `@-` revset expression instead. The `git_head` template
+ keyword now returns a boolean.
 
 * Help command doesn't work recursively anymore, i.e. `jj workspace help root`
  doesn't work anymore.

cli/src/commit_templater.rs

@@ -30,7 +30,6 @@ use jj_lib::extensions_map::ExtensionsMap;
 use jj_lib::fileset;
 use jj_lib::fileset::FilesetDiagnostics;
 use jj_lib::fileset::FilesetExpression;
-use jj_lib::git;
 use jj_lib::id_prefix::IdPrefixContext;
 use jj_lib::id_prefix::IdPrefixIndex;
 use jj_lib::matchers::Matcher;
@@ -703,8 +702,11 @@ fn builtin_commit_methods<'repo>() -> CommitTemplateBuildMethodFnMap<'repo, Comm
  |language, _diagnostics, _build_ctx, self_property, function| {
  function.expect_no_arguments()?;
  let repo = language.repo;
- let out_property = self_property.map(|commit| extract_git_head(repo, &commit));
- Ok(L::wrap_ref_name_opt(out_property))
+ let out_property = self_property.map(|commit| {
+ let target = repo.view().git_head();
+ target.added_ids().contains(commit.id())
+ });
+ Ok(L::wrap_boolean(out_property))
  },
  );
  map.insert(
@@ -1230,14 +1232,6 @@ fn build_ref_names_index<'a>(
  index
 }
 
-fn extract_git_head(repo: &dyn Repo, commit: &Commit) -> Option<Rc<RefName>> {
- let target = repo.view().git_head();
- target
- .added_ids()
- .contains(commit.id())
- .then(|| RefName::remote_only("HEAD", git::REMOTE_NAME_FOR_LOCAL_GIT_REPO, target.clone()))
-}
-
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum CommitOrChangeId {
  Commit(CommitId),

cli/src/config/templates.toml

@@ -78,7 +78,7 @@ if(root,
  bookmarks,
  tags,
  working_copies,
- git_head,
+ if(git_head, label("git_head", "git_head()")),
  format_short_commit_id(commit_id),
  if(conflict, label("conflict", "conflict")),
  if(empty, label("empty", "(empty)")),
@@ -103,7 +103,7 @@ if(root,
  bookmarks,
  tags,
  working_copies,
- git_head,
+ if(git_head, label("git_head", "git_head()")),
  format_short_commit_id(commit_id),
  if(conflict, label("conflict", "conflict")),
  ) ++ "\n",

cli/tests/test_commit_template.rs

@@ -671,27 +671,21 @@ fn test_log_git_head() {
  test_env.jj_cmd_ok(&repo_path, &["new", "-m=initial"]);
  std::fs::write(repo_path.join("file"), "foo\n").unwrap();
 
- let template = r#"
- separate(", ",
- if(git_head, "name: " ++ git_head.name()),
- "remote: " ++ git_head.remote(),
- ) ++ "\n"
- "#;
- let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-T", template]);
- insta::assert_snapshot!(stdout, @r###"
- @ remote: <Error: No RefName available>
- ○ name: HEAD, remote: git
- ◆ remote: <Error: No RefName available>
- "###);
+ let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-T", "git_head"]);
+ insta::assert_snapshot!(stdout, @r#"
+ @ false
+ ○ true
+ ◆ false
+ "#);
 
  let stdout = test_env.jj_cmd_success(&repo_path, &["log", "--color=always"]);
- insta::assert_snapshot!(stdout, @r###"
+ insta::assert_snapshot!(stdout, @r#"
  @ rlvkpnrz [38;5;[email protected] 2001-02-03 08:05:09 50aaf475
  │ initial
- ○ [1m[38;5;5mq[0m[38;5;8mpvuntsm[39m [38;5;[email protected][39m [38;5;6m2001-02-03 08:05:07[39m [38;5;2mHEAD@git[39m [1m[38;5;4m2[0m[38;5;8m30dd059[39m
+ ○ [1m[38;5;5mq[0m[38;5;8mpvuntsm[39m [38;5;[email protected][39m [38;5;6m2001-02-03 08:05:07[39m [38;5;2mgit_head()[39m [1m[38;5;4m2[0m[38;5;8m30dd059[39m
  │ (empty) (no description set)
  ◆ zzzzzzzz root() 00000000
- "###);
+ "#);
 }
 
 #[test]