feat(args): add --output argument

README.md

@@ -29,6 +29,7 @@ git-cliff [FLAGS] [OPTIONS] [RANGE]
 -w, --workdir <PATH>       Sets the working directory [env: WORKDIR=]
 -r, --repository <PATH>    Sets the repository to parse commits from [env: REPOSITORY=]
 -p, --changelog <PATH>     Prepends entries to the given changelog file [env: CHANGELOG=]
+-o, --output <PATH>        Writes output to the given file [env: OUTPUT=]
 -t, --tag <TAG>            Sets the tag for the latest version [env: TAG=]
 -s, --strip <PART>         Strips the given parts from the changelog [possible values: header, footer, all]
 ```

git-cliff/src/args.rs

@@ -38,6 +38,9 @@ pub struct Opt {
 	/// Prepends entries to the given changelog file.
 	#[structopt(short = "p", long, env, value_name = "PATH")]
 	pub changelog:  Option<PathBuf>,
+	/// Writes output to the given file.
+	#[structopt(short, long, env, value_name = "PATH")]
+	pub output:     Option<PathBuf>,
 	/// Sets the tag for the latest version.
 	#[structopt(short, long, env, value_name = "TAG", allow_hyphen_values = true)]
 	pub tag:        Option<String>,

git-cliff/src/lib.rs

@@ -128,6 +128,8 @@ pub fn run(mut args: Opt) -> Result<()> {
 	let changelog = Changelog::new(releases, &config)?;
 	if let Some(path) = args.changelog {
 		changelog.prepend(fs::read_to_string(&path)?, &mut File::create(path)?)
+	} else if let Some(path) = args.output {
+		changelog.generate(&mut File::create(path)?)
 	} else {
 		changelog.generate(&mut io::stdout())
 	}