templater: indicate if branch needs to be pushed to a remote

It's useful to know when you've modified a branch that exists on a
remote. A typical case is when you have pushed a branch to a remote
and then rewritten it. This commit adds an indication in the
`branches` template keyword. A branch that needs to be pushed to a
remote now has a `*` at the end (similar to how conflicted branches
have a `?` at the end). Note that the indication only considers
remotes where the branch currently exists, so there won't be an
indication that the branch has not been pushed to a remote.

Closes #254

CHANGELOG.md

···
 * (#469) `jj git` subcommands will prompt for credentials when
   required for HTTPS remotes rather than failing.
 
+* (#254) Branches that have a different target on some remote than they do
+  locally are now indicated by an asterisk suffix (e.g. `main*`) in `jj log`.
+
 ### Fixed bugs
 
 * `jj edit root` now fails gracefully.

docs/branches.md

···
 
 Jujutsu also records the last seen position on each remote (just like Git's
 remote-tracking branches). You can refer to these with
-`<branch name>@<remote name>`, such as `jj co main@origin`. Most commands don't
+`<branch name>@<remote name>`, such as `jj new main@origin`. Most commands don't
 show the remote branch if it has the same target as the local branch. The local
 branch (without `@<remote name>`) is considered the branch's desired target.
 Consequently, if you want to update a branch on a remote, you first update the
-branch locally and then push the update to the remote.
+branch locally and then push the update to the remote. If a local branch also
+exists on some remote but points to a different target there, `jj log` will
+show the branch name with an asterisk suffix (e.g. `main*`). That is meant to
+remind you that you may want to push the branch to some remote.
 
 When you pull from a remote, any changes compared to the current record of the
 remote's state will be propagated to the local branch. Let's say you run

src/templater.rs

···
                 if local_target.has_add(context.id()) {
                     if local_target.is_conflict() {
                         names.push(format!("{}?", branch_name));
+                    } else if branch_target
+                        .remote_targets
+                        .values()
+                        .any(|remote_target| remote_target != local_target)
+                    {
+                        names.push(format!("{}*", branch_name));
                     } else {
                         names.push(branch_name.clone());
                     }

tests/test_templater.rs

···
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use crate::common::TestEnvironment;
+
+pub mod common;
+
+#[test]
+fn test_templater_branches() {
+    let test_env = TestEnvironment::default();
+
+    test_env.jj_cmd_success(test_env.env_root(), &["init", "--git", "origin"]);
+    let origin_path = test_env.env_root().join("origin");
+    let origin_git_repo_path = origin_path
+        .join(".jj")
+        .join("repo")
+        .join("store")
+        .join("git");
+    // TODO: This initial export shouldn't be needed
+    test_env.jj_cmd_success(&origin_path, &["git", "export"]);
+
+    // Created some branches on the remote
+    test_env.jj_cmd_success(&origin_path, &["describe", "-m=description 1"]);
+    test_env.jj_cmd_success(&origin_path, &["branch", "create", "branch1"]);
+    test_env.jj_cmd_success(&origin_path, &["new", "root", "-m=description 2"]);
+    test_env.jj_cmd_success(&origin_path, &["branch", "create", "branch2"]);
+    test_env.jj_cmd_success(&origin_path, &["new", "root", "-m=description 3"]);
+    test_env.jj_cmd_success(&origin_path, &["branch", "create", "branch3"]);
+    test_env.jj_cmd_success(&origin_path, &["git", "export"]);
+    test_env.jj_cmd_success(
+        test_env.env_root(),
+        &[
+            "git",
+            "clone",
+            origin_git_repo_path.to_str().unwrap(),
+            "local",
+        ],
+    );
+    let workspace_root = test_env.env_root().join("local");
+
+    // Rewrite branch1, move branch2 forward, create conflict in branch3, add
+    // new-branch
+    test_env.jj_cmd_success(
+        &workspace_root,
+        &["describe", "branch1", "-m", "modified branch1 commit"],
+    );
+    test_env.jj_cmd_success(&workspace_root, &["new", "branch2"]);
+    test_env.jj_cmd_success(&workspace_root, &["branch", "set", "branch2"]);
+    test_env.jj_cmd_success(&workspace_root, &["branch", "create", "new-branch"]);
+    test_env.jj_cmd_success(&workspace_root, &["describe", "branch3", "-m=local"]);
+    test_env.jj_cmd_success(&origin_path, &["describe", "branch3", "-m=origin"]);
+    test_env.jj_cmd_success(&origin_path, &["git", "export"]);
+    test_env.jj_cmd_success(&workspace_root, &["git", "fetch"]);
+
+    let output = test_env.jj_cmd_success(
+        &workspace_root,
+        &["log", "-T", r#"commit_id.short() " " branches"#],
+    );
+    insta::assert_snapshot!(output, @r###"
+    o 212985c08a44 branch3?
+    | @ cbf02da4e154 branch2* new-branch
+    | | o c794a4eab3b9 branch1*
+    | |/  
+    |/|   
+    | o 8cd8e5dc9595 branch2@origin
+    |/  
+    o 000000000000 
+    "###);
+}