cli: add test of --no-commit-working-copy

I didn't add a test in #90 because the test cases needed to be cleaned
up first. They now look a bit better, so we can add test for the
flag.

src/testutils.rs

@@ -55,11 +55,15 @@ impl TestEnvironment {
     }
 }
 
+pub fn get_stdout_string(assert: &assert_cmd::assert::Assert) -> String {
+    String::from_utf8(assert.get_output().stdout.clone()).unwrap()
+}
+
 pub fn capture_matches(
     assert: assert_cmd::assert::Assert,
     pattern: &str,
 ) -> (assert_cmd::assert::Assert, Vec<String>) {
-    let stdout_string = String::from_utf8(assert.get_output().stdout.clone()).unwrap();
+    let stdout_string = get_stdout_string(&assert);
     let assert = assert.stdout(predicates::str::is_match(pattern).unwrap());
     let matches = Regex::new(pattern)
         .unwrap()

tests/test_global_opts.rs

@@ -0,0 +1,53 @@
+// 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 jujutsu::testutils::{get_stdout_string, TestEnvironment};
+
+#[test]
+fn test_no_commit_working_copy() {
+    let test_env = TestEnvironment::default();
+    test_env
+        .jj_cmd(test_env.env_root(), &["init", "repo"])
+        .assert()
+        .success();
+
+    let repo_path = test_env.env_root().join("repo");
+
+    std::fs::write(repo_path.join("file"), "initial").unwrap();
+    let assert = test_env
+        .jj_cmd(&repo_path, &["log", "-T", "commit_id"])
+        .assert()
+        .success();
+    let initial_commit_id_hex = get_stdout_string(&assert);
+
+    // Modify the file. With --no-commit-working-copy, we still get the same commit
+    // ID.
+    std::fs::write(repo_path.join("file"), "modified").unwrap();
+    let assert = test_env
+        .jj_cmd(
+            &repo_path,
+            &["log", "-T", "commit_id", "--no-commit-working-copy"],
+        )
+        .assert()
+        .success();
+    let still_initial_commit_id_hex = get_stdout_string(&assert);
+    assert_eq!(still_initial_commit_id_hex, initial_commit_id_hex);
+    // But without --no-commit-working-copy, we get a new commit ID.
+    let assert = test_env
+        .jj_cmd(&repo_path, &["log", "-T", "commit_id"])
+        .assert()
+        .success();
+    let modified_commit_id_hex = get_stdout_string(&assert);
+    assert_ne!(modified_commit_id_hex, initial_commit_id_hex);
+}