feat(config): make the changelog section optional (#45)

git-cliff-core/src/config.rs

@@ -5,19 +5,22 @@ use regex::Regex;
 #[derive(Debug, Clone, serde_derive::Serialize, serde_derive::Deserialize)]
 pub struct Config {
 	/// Configuration values about changelog generation.
+	#[serde(default)]
 	pub changelog: ChangelogConfig,
 	/// Configuration values about git.
 	#[serde(default)]
 	pub git:       GitConfig,
 }
 
 /// Changelog configuration.
-#[derive(Debug, Clone, serde_derive::Serialize, serde_derive::Deserialize)]
+#[derive(
+	Debug, Default, Clone, serde_derive::Serialize, serde_derive::Deserialize,
+)]
 pub struct ChangelogConfig {
 	/// Changelog header.
 	pub header: Option<String>,
 	/// Changelog body, template.
-	pub body:   String,
+	pub body:   Option<String>,
 	/// Changelog footer.
 	pub footer: Option<String>,
 	/// Trim the template.

git-cliff/src/changelog.rs

@@ -1,6 +1,9 @@
 use git_cliff_core::commit::Commit;
 use git_cliff_core::config::Config;
-use git_cliff_core::error::Result;
+use git_cliff_core::error::{
+	Error,
+	Result,
+};
 use git_cliff_core::release::Release;
 use git_cliff_core::template::Template;
 use std::io::Write;
@@ -16,19 +19,27 @@ pub struct Changelog<'a> {
 impl<'a> Changelog<'a> {
 	/// Constructs a new instance.
 	pub fn new(releases: Vec<Release<'a>>, config: &'a Config) -> Result<Self> {
+		let mut template = config
+			.changelog
+			.body
+			.as_deref()
+			.unwrap_or_default()
+			.to_string();
+		if template.is_empty() {
+			return Err(Error::ChangelogError(String::from(
+				"changelog body cannot be empty",
+			)));
+		}
+		if config.changelog.trim.unwrap_or(true) {
+			template = template
+				.lines()
+				.map(|v| v.trim())
+				.collect::<Vec<&str>>()
+				.join("\n")
+		}
 		let mut changelog = Self {
 			releases,
-			template: Template::new({
-				let mut template = config.changelog.body.to_string();
-				if config.changelog.trim.unwrap_or(true) {
-					template = template
-						.lines()
-						.map(|v| v.trim())
-						.collect::<Vec<&str>>()
-						.join("\n")
-				}
-				template
-			})?,
+			template: Template::new(template)?,
 			config,
 		};
 		changelog.process_commits();

git-cliff/src/lib.rs

@@ -63,12 +63,17 @@ pub fn run(mut args: Opt) -> Result<()> {
 		}
 	}
 
+	// Load the default configuration if necessary.
 	let mut config = if fs::metadata(&path).is_ok() {
 		Config::parse(path)?
 	} else {
 		warn!("{:?} is not found, using the default configuration.", path);
 		EmbeddedConfig::parse()?
 	};
+	if config.changelog.body.is_none() {
+		warn!("Changelog body is not specified, using the default template.");
+		config.changelog.body = EmbeddedConfig::parse()?.changelog.body;
+	}
 
 	// Update the configuration based on command line arguments and vice versa.
 	match args.strip.as_deref() {
@@ -92,8 +97,8 @@ pub fn run(mut args: Opt) -> Result<()> {
 			)));
 		}
 	}
-	if let Some(template) = args.body {
-		config.changelog.body = template;
+	if args.body.is_some() {
+		config.changelog.body = args.body;
 	}
 	if args.sort == "oldest" {
 		if let Some(ref sort_commits) = config.git.sort_commits {