feat(config): support a global location for configuration file (#2)

README.md

@@ -233,7 +233,13 @@ Also, see the [continuous deployment workflow](./.github/workflows/cd.yml) of th
 
 **git-cliff** configuration file supports [TOML](https://github.com/toml-lang/toml) (preferred) and [YAML](https://yaml.org) formats.
 
-See [config/cliff.toml](./config/cliff.toml) for an example.
+The configuration file is read from `$HOME/git-cliff/cliff.toml` if the file exists. This location depends on the platform, for example:
+
+- on Linux: `/home/<user>/.config/git-cliff/cliff.toml`
+- on Windows: `C:\Users\<user>\AppData\Roaming\git-cliff\cliff.toml`
+- on macOS: `/Users/<user>/Library/Application Support/git-cliff/cliff.toml`
+
+See [config/cliff.toml](./config/cliff.toml) for the default configuration values.
 
 ### changelog
 

git-cliff/Cargo.toml

@@ -19,6 +19,7 @@ path = "src/bin/completions.rs"
 [dependencies]
 pretty_env_logger = "0.4.0"
 log = "0.4.14"
+dirs-next = "2.0.0"
 
 [dependencies.git-cliff-core]
 version = "0.1.2" # managed by release.sh

git-cliff/src/lib.rs

@@ -46,14 +46,24 @@ pub fn run(mut args: Opt) -> Result<()> {
 		}
 	}
 
-	// Parse configuration file.
-	let path = match args.config.to_str() {
+	// Parse the configuration file.
+	let mut path = match args.config.to_str() {
 		Some(v) => Ok(v.to_string()),
 		None => Err(Error::IoError(io::Error::new(
 			io::ErrorKind::Other,
 			"path contains invalid characters",
 		))),
 	}?;
+	if let Some(config_path) = dirs_next::config_dir()
+		.map(|dir| dir.join(env!("CARGO_PKG_NAME")).join(DEFAULT_CONFIG))
+		.map(|path| path.to_str().map(String::from))
+		.flatten()
+	{
+		if fs::metadata(&config_path).is_ok() {
+			path = config_path;
+		}
+	}
+
 	let mut config = if fs::metadata(&path).is_ok() {
 		Config::parse(path)?
 	} else {