cli: allow overwriting non-scalar with jj config set

Before this patch, it was an error to run `jj config set --user foo
'[1]'` twice. But it's only been broken since the previous commit
because '[1]' was interpreted as a string before then.

cli/src/cli_util.rs

@@ -2199,13 +2199,13 @@ pub fn write_config_value_to_file(
                 ))
             })?;
     }
-    // Error out if overwriting non-scalar value for key (table or array).
+    // Error out if overwriting non-scalar value for key (table or array) with
+    // scalar.
     match target_table.get(last_key_part) {
-        None | Some(toml_edit::Item::None) => {}
-        Some(toml_edit::Item::Value(val)) if !val.is_array() && !val.is_inline_table() => {}
-        _ => {
+        None | Some(toml_edit::Item::None | toml_edit::Item::Value(_)) => {}
+        Some(toml_edit::Item::Table(_) | toml_edit::Item::ArrayOfTables(_)) => {
             return Err(user_error(format!(
-                "Failed to set {key}: would overwrite entire non-scalar value with scalar"
+                "Failed to set {key}: would overwrite entire table"
             )));
         }
     }

cli/tests/test_config_command.rs

@@ -340,7 +340,7 @@ fn test_config_set_for_repo() {
 #[test]
 fn test_config_set_toml_types() {
     let mut test_env = TestEnvironment::default();
-    test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
+    test_env.jj_cmd_ok(test_env.env_root(), &["init", "repo", "--git"]);
     let user_config_path = test_env.config_path().join("config.toml");
     test_env.set_config_path(user_config_path.clone());
     let repo_path = test_env.env_root().join("repo");
@@ -382,8 +382,26 @@ fn test_config_set_type_mismatch() {
         &["config", "set", "--user", "test-table", "not-a-table"],
     );
     insta::assert_snapshot!(stderr, @r###"
-    Error: Failed to set test-table: would overwrite entire non-scalar value with scalar
+    Error: Failed to set test-table: would overwrite entire table
     "###);
+
+    // But it's fine to overwrite arrays and inline tables
+    test_env.jj_cmd_success(
+        &repo_path,
+        &["config", "set", "--user", "test-table.array", "[1,2,3]"],
+    );
+    test_env.jj_cmd_success(
+        &repo_path,
+        &["config", "set", "--user", "test-table.array", "[4,5,6]"],
+    );
+    test_env.jj_cmd_success(
+        &repo_path,
+        &["config", "set", "--user", "test-table.inline", "{ x = 42}"],
+    );
+    test_env.jj_cmd_success(
+        &repo_path,
+        &["config", "set", "--user", "test-table.inline", "42"],
+    );
 }
 
 #[test]