config: use XDG_CONFIG_HOME on MacOS as a fallback

This replaces the `dirs` crate with the more lightweight and flexible `etcetera` crate,
which also lets us use XDG config on MacOS.

Fixes #3434

CHANGELOG.md

@@ -27,6 +27,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * `jj status` now supports filtering by paths. For example, `jj status .` will
   only list changed files that are descendants of the current directory.
 
+* On MacOS, jj will now look for its config in `$XDG_CONFIG_HOME` first, then fall back to `~/Library/Application Support`
+
 ### Fixed bugs
 
 ## [0.16.0] - 2024-04-03

Cargo.toml

@@ -43,9 +43,9 @@ config = { version = "0.13.4", default-features = false, features = ["toml"] }
 criterion = "0.5.1"
 crossterm = { version = "0.27", default-features = false }
 digest = "0.10.7"
-dirs = "5.0.1"
 either = "1.10.0"
 esl01-renderdag = "0.3.0"
+etcetera = "0.8.0"
 futures = "0.3.30"
 git2 = "0.18.3"
 gix = { version = "0.61.0", default-features = false, features = [

cli/Cargo.toml

@@ -43,8 +43,8 @@ clap_mangen = { workspace = true }
 config = { workspace = true }
 criterion = { workspace = true, optional = true }
 crossterm = { workspace = true }
-dirs = { workspace = true }
 esl01-renderdag = { workspace = true }
+etcetera = { workspace = true }
 futures = { workspace = true }
 git2 = { workspace = true }
 gix = { workspace = true }

cli/src/config.rs

@@ -19,6 +19,7 @@ use std::process::Command;
 use std::{env, fmt};
 
 use config::Source;
+use etcetera::BaseStrategy;
 use itertools::Itertools;
 use jj_lib::settings::ConfigResultExt as _;
 use thiserror::Error;
@@ -251,8 +252,8 @@ struct ConfigEnv {
 impl ConfigEnv {
     fn new() -> Self {
         ConfigEnv {
-            config_dir: dirs::config_dir(),
-            home_dir: dirs::home_dir(),
+            config_dir: config_dir(),
+            home_dir: etcetera::home_dir().ok(),
             jj_config: env::var("JJ_CONFIG").ok(),
         }
     }
@@ -434,6 +435,41 @@ fn read_config_path(config_path: &Path) -> Result<config::Config, config::Config
         .build()
 }
 
+#[cfg(target_os = "macos")]
+fn config_dir() -> Option<PathBuf> {
+    // Define a closure to check if config file exists in a directory
+    let check_config = |dir: &Path| {
+        let mut config_file = dir.to_owned();
+        config_file.push("jj/config.toml");
+        if config_file.exists() {
+            Some(dir.to_owned())
+        } else {
+            None
+        }
+    };
+
+    // Try getting config directory from Xdg base strategy first.
+    let path = etcetera::base_strategy::Xdg::new()
+        .ok()
+        .and_then(|strategy| check_config(&strategy.config_dir()));
+
+    // If config directory is not found from Xdg, try Apple instead. `Application
+    // Support` is really the data_dir, so get that.
+    path.or_else(|| {
+        etcetera::base_strategy::Apple::new()
+            .ok()
+            .and_then(|strategy| check_config(&strategy.data_dir()))
+    })
+}
+
+#[cfg(not(target_os = "macos"))]
+/// For anything but MacOS, use the default config dir for the platform
+fn config_dir() -> Option<PathBuf> {
+    etcetera::choose_base_strategy()
+        .ok()
+        .map(|strategy| strategy.config_dir())
+}
+
 /// Command name and arguments specified by config.
 #[derive(Clone, Debug, Eq, PartialEq, serde::Deserialize)]
 #[serde(untagged)]

cli/src/git_util.rs

@@ -121,7 +121,7 @@ fn pinentry_get_pw(url: &str) -> Option<String> {
 #[tracing::instrument]
 fn get_ssh_keys(_username: &str) -> Vec<PathBuf> {
     let mut paths = vec![];
-    if let Some(home_dir) = dirs::home_dir() {
+    if let Ok(home_dir) = etcetera::home_dir() {
         let ssh_dir = Path::new(&home_dir).join(".ssh");
         for filename in ["id_ed25519_sk", "id_ed25519", "id_rsa"] {
             let key_path = ssh_dir.join(filename);

docs/config.md

@@ -745,10 +745,10 @@ platform-specific location is recommended for better integration with platform
 services. It is an error for both of these files to exist.
 
 | Platform | Value                                              | Example                                                   |
-| :------- | :------------------------------------------------- | :-------------------------------------------------------- |
-| Linux    | `$XDG_CONFIG_HOME/jj/config.toml`                  | `/home/alice/.config/jj/config.toml`                      |
-| macOS    | `$HOME/Library/Application Support/jj/config.toml` | `/Users/Alice/Library/Application Support/jj/config.toml` |
-| Windows  | `{FOLDERID_RoamingAppData}\jj\config.toml`         | `C:\Users\Alice\AppData\Roaming\jj\config.toml`           |
+| :------- | -------------------------------------------------- | --------------------------------------------------------- |
+| Linux    | `$XDG_CONFIG_HOME/jj/config.toml`                    | `/home/alice/.config/jj/config.toml`                        |
+| macOS    | `$HOME/Library/Application Support/jj/config.toml` or `$XDG_CONFIG_HOME/jj/config.toml` as fallback | `/Users/Alice/Library/Application Support/jj/config.toml` or `/Users/Alice/.config/jj/config.toml` |
+| Windows  | `{FOLDERID_RoamingAppData}\jj\config.toml`           | `C:\Users\Alice\AppData\Roaming\jj\config.toml`             |
 
 The location of the `jj` config file can also be overridden with the
 `JJ_CONFIG` environment variable. If it is not empty, it should contain the path