templater: expose RefTarget methods through RefName type

I considered adding RefTarget template type, but some of the methods naturally
fit to RefName. For example, a conflicted branch name is decorated as "??", so
it makes sense to add branch.conflict() instead of branch.target().conflict().

I'm not pretty sure how many RefName methods we'll need to add to port the
current branch listing, but there will be .tracked(), .tracking_local_present(),
.ahead_by(), and .behind_by().

cli/src/commit_templater.rs

@@ -757,6 +757,10 @@ impl RefName {
         self.remote.is_some()
     }
 
+    fn is_present(&self) -> bool {
+        self.target.is_present()
+    }
+
     /// Whether the ref target has conflicts.
     fn has_conflict(&self) -> bool {
         self.target.has_conflict()
@@ -805,6 +809,58 @@ fn builtin_ref_name_methods<'repo>() -> CommitTemplateBuildMethodFnMap<'repo, Re
             Ok(L::wrap_string(out_property))
         },
     );
+    map.insert(
+        "present",
+        |_language, _build_ctx, self_property, function| {
+            template_parser::expect_no_arguments(function)?;
+            let out_property = self_property.map(|ref_name| ref_name.is_present());
+            Ok(L::wrap_boolean(out_property))
+        },
+    );
+    map.insert(
+        "conflict",
+        |_language, _build_ctx, self_property, function| {
+            template_parser::expect_no_arguments(function)?;
+            let out_property = self_property.map(|ref_name| ref_name.has_conflict());
+            Ok(L::wrap_boolean(out_property))
+        },
+    );
+    map.insert(
+        "normal_target",
+        |language, _build_ctx, self_property, function| {
+            template_parser::expect_no_arguments(function)?;
+            let repo = language.repo;
+            let out_property = self_property.and_then(|ref_name| {
+                let maybe_id = ref_name.target.as_normal();
+                Ok(maybe_id.map(|id| repo.store().get_commit(id)).transpose()?)
+            });
+            Ok(L::wrap_commit_opt(out_property))
+        },
+    );
+    map.insert(
+        "removed_targets",
+        |language, _build_ctx, self_property, function| {
+            template_parser::expect_no_arguments(function)?;
+            let repo = language.repo;
+            let out_property = self_property.and_then(|ref_name| {
+                let ids = ref_name.target.removed_ids();
+                Ok(ids.map(|id| repo.store().get_commit(id)).try_collect()?)
+            });
+            Ok(L::wrap_commit_list(out_property))
+        },
+    );
+    map.insert(
+        "added_targets",
+        |language, _build_ctx, self_property, function| {
+            template_parser::expect_no_arguments(function)?;
+            let repo = language.repo;
+            let out_property = self_property.and_then(|ref_name| {
+                let ids = ref_name.target.added_ids();
+                Ok(ids.map(|id| repo.store().get_commit(id)).try_collect()?)
+            });
+            Ok(L::wrap_commit_list(out_property))
+        },
+    );
     map
 }
 

cli/tests/test_tag_command.rs

@@ -35,44 +35,79 @@ fn test_tag_list() {
     test_env.jj_cmd_ok(&repo_path, &["branch", "create", "branch1"]);
     test_env.jj_cmd_ok(&repo_path, &["new", "root()", "-mcommit2"]);
     test_env.jj_cmd_ok(&repo_path, &["branch", "create", "branch2"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "root()", "-mcommit3"]);
+    test_env.jj_cmd_ok(&repo_path, &["branch", "create", "branch3"]);
     test_env.jj_cmd_ok(&repo_path, &["git", "export"]);
 
     copy_ref("refs/heads/branch1", "refs/tags/test_tag");
     copy_ref("refs/heads/branch2", "refs/tags/test_tag2");
+    copy_ref("refs/heads/branch1", "refs/tags/conflicted_tag");
     test_env.jj_cmd_ok(&repo_path, &["git", "import"]);
+    copy_ref("refs/heads/branch2", "refs/tags/conflicted_tag");
+    test_env.jj_cmd_ok(&repo_path, &["git", "import"]);
+    copy_ref("refs/heads/branch3", "refs/tags/conflicted_tag");
+    test_env.jj_cmd_ok(&repo_path, &["git", "import", "--at-op=@-"]);
+    test_env.jj_cmd_ok(&repo_path, &["status"]); // resolve concurrent ops
 
     insta::assert_snapshot!(
         test_env.jj_cmd_success(&repo_path, &["tag", "list"]),
         @r###"
-        test_tag
-        test_tag2
-         "###);
+    conflicted_tag
+    test_tag
+    test_tag2
+    "###);
 
-     insta::assert_snapshot!(
-         test_env.jj_cmd_success(&repo_path, &["tag", "list", "--color=always"]),
-         @r###"
-     test_tag
-     test_tag2
-     "###);
+    insta::assert_snapshot!(
+        test_env.jj_cmd_success(&repo_path, &["tag", "list", "--color=always"]),
+        @r###"
+    conflicted_tag
+    test_tag
+    test_tag2
+    "###);
 
     // Test pattern matching.
     insta::assert_snapshot!(
         test_env.jj_cmd_success(&repo_path, &["tag", "list", "test_tag2"]),
         @r###"
-        test_tag2
-         "###);
+    test_tag2
+    "###);
 
     insta::assert_snapshot!(
         test_env.jj_cmd_success(&repo_path, &["tag", "list", "glob:test_tag?"]),
         @r###"
-        test_tag2
-         "###);
+    test_tag2
+    "###);
 
-    let template = r#"'name: ' ++ name ++ "\n""#;
+    let template = r#"
+    concat(
+      "[" ++ name ++ "]\n",
+      separate(" ", "present:", present) ++ "\n",
+      separate(" ", "conflict:", conflict) ++ "\n",
+      separate(" ", "normal_target:", normal_target.description().first_line()) ++ "\n",
+      separate(" ", "removed_targets:", removed_targets.map(|c| c.description().first_line())) ++ "\n",
+      separate(" ", "added_targets:", added_targets.map(|c| c.description().first_line())) ++ "\n",
+    )
+    "#;
     insta::assert_snapshot!(
         test_env.jj_cmd_success(&repo_path, &["tag", "list", "-T", template]),
         @r###"
-    name: test_tag
-    name: test_tag2
+    [conflicted_tag]
+    present: true
+    conflict: true
+    normal_target: <Error: No commit available>
+    removed_targets: commit1
+    added_targets: commit2 commit3
+    [test_tag]
+    present: true
+    conflict: false
+    normal_target: commit1
+    removed_targets:
+    added_targets: commit1
+    [test_tag2]
+    present: true
+    conflict: false
+    normal_target: commit2
+    removed_targets:
+    added_targets: commit2
     "###);
 }

docs/templates.md

@@ -155,6 +155,14 @@ The following methods are defined.
 
 * `.name() -> String`: Local branch or tag name.
 * `.remote() -> String`: Remote name or empty if this is a local ref.
+* `.present() -> Boolean`: True if the ref points to any commit.
+* `.conflict() -> Boolean`: True if [the branch or tag is
+  conflicted](branches.md#conflicts).
+* `.normal_target() -> Option<Commit>`: Target commit if the ref is not
+  conflicted and points to a commit.
+* `.removed_targets() -> List<Commit>`: Old target commits if conflicted.
+* `.added_targets() -> List<Commit>`: New target commits. The list usually
+  contains one "normal" target.
 
 ### ShortestIdPrefix type