config: load system host/user name by CLI and insert as env-base layer

Since the default now falls back to "", we can simply override the default by
CLI. We don't have to touch the environment in jj-lib.

Cargo.lock

@@ -2056,7 +2056,6 @@ dependencies = [
  "tracing",
  "version_check",
  "watchman_client",
- "whoami",
  "winreg",
  "zstd",
 ]

cli/src/config.rs

@@ -438,9 +438,23 @@ pub fn config_from_environment(default_layers: impl IntoIterator<Item = ConfigLa
     RawConfig(config)
 }
 
+const OP_HOSTNAME: &str = "operation.hostname";
+const OP_USERNAME: &str = "operation.username";
+
 /// Environment variables that should be overridden by config values
 fn env_base_layer() -> ConfigLayer {
     let mut layer = ConfigLayer::empty(ConfigSource::EnvBase);
+    // TODO: warn if hostname/username is empty after loading config files?
+    if let Ok(value) = whoami::fallible::hostname()
+        .inspect_err(|err| tracing::warn!(?err, "failed to get hostname"))
+    {
+        layer.set_value(OP_HOSTNAME, value).unwrap();
+    }
+    if let Ok(value) = whoami::fallible::username()
+        .inspect_err(|err| tracing::warn!(?err, "failed to get username"))
+    {
+        layer.set_value(OP_USERNAME, value).unwrap();
+    }
     if !env::var("NO_COLOR").unwrap_or_default().is_empty() {
         // "User-level configuration files and per-instance command-line arguments
         // should override $NO_COLOR." https://no-color.org/
@@ -496,10 +510,10 @@ fn env_overrides_layer() -> ConfigLayer {
         layer.set_value("debug.operation-timestamp", value).unwrap();
     }
     if let Ok(value) = env::var("JJ_OP_HOSTNAME") {
-        layer.set_value("operation.hostname", value).unwrap();
+        layer.set_value(OP_HOSTNAME, value).unwrap();
     }
     if let Ok(value) = env::var("JJ_OP_USERNAME") {
-        layer.set_value("operation.username", value).unwrap();
+        layer.set_value(OP_USERNAME, value).unwrap();
     }
     if let Ok(value) = env::var("JJ_EDITOR") {
         layer.set_value("ui.editor", value).unwrap();

cli/tests/test_global_opts.rs

@@ -834,9 +834,15 @@ fn test_default_config() {
         maskable_re.is_match(&hostname) && maskable_re.is_match(&username)
     };
 
-    let (stdout, stderr) = jj_cmd_ok(test_env.env_root(), &["config", "list"]);
-    insta::assert_snapshot!(stdout, @"");
-    insta::assert_snapshot!(stderr, @"Warning: No config to list");
+    let (stdout, stderr) = jj_cmd_ok(
+        test_env.env_root(),
+        &["config", "list", r#"-Tname ++ "\n""#],
+    );
+    insta::assert_snapshot!(stdout, @r"
+    operation.hostname
+    operation.username
+    ");
+    insta::assert_snapshot!(stderr, @"");
 
     let repo_path = test_env.env_root().join("repo");
     let (stdout, stderr) = jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);

lib/Cargo.toml

@@ -74,7 +74,6 @@ tokio = { workspace = true, optional = true }
 toml_edit = { workspace = true }
 tracing = { workspace = true }
 watchman_client = { workspace = true, optional = true }
-whoami = { workspace = true }
 zstd = { workspace = true }
 
 [target.'cfg(unix)'.dependencies]

lib/src/config/misc.toml

@@ -14,8 +14,8 @@ abandon-unreachable-commits = true
 # auto-local-bookmark = false
 
 [operation]
-# hostname = <host>
-# username = <user>
+hostname = ""
+username = ""
 
 [signing]
 backend = "none"

lib/src/settings.rs

@@ -152,21 +152,8 @@ impl UserSettings {
         let operation_timestamp = config
             .get_value_with("debug.operation-timestamp", to_timestamp)
             .optional()?;
-        // Instead of handling environment data here, it might be better to load
-        // them by CLI and insert as a config layer.
-        // TODO: warn empty hostname/username by CLI?
-        let operation_hostname = config
-            .get("operation.hostname")
-            .optional()?
-            .map_or_else(whoami::fallible::hostname, Ok)
-            .inspect_err(|err| tracing::warn!(?err, "operation.hostname couldn't be set"))
-            .unwrap_or_default();
-        let operation_username = config
-            .get("operation.username")
-            .optional()?
-            .map_or_else(whoami::fallible::username, Ok)
-            .inspect_err(|err| tracing::warn!(?err, "operation.username couldn't be set"))
-            .unwrap_or_default();
+        let operation_hostname = config.get("operation.hostname")?;
+        let operation_username = config.get("operation.username")?;
         let data = UserSettingsData {
             user_name,
             user_email,