fix(changelog): return error if there is not a latest tag to process

git-cliff-core/src/error.rs

@@ -19,6 +19,9 @@ pub enum Error {
 	/// Error that may occur while grouping commits.
 	#[error("Grouping error: `{0}`")]
 	GroupError(String),
+	/// Error that may occur while generating changelog.
+	#[error("Changelog error: `{0}`")]
+	ChangelogError(String),
 	/// Error that may occur while template operations such as parse and render.
 	#[error("Template error: `{0}`")]
 	TemplateError(#[from] tera::Error),

git-cliff/src/lib.rs

@@ -86,7 +86,11 @@ pub fn run(mut args: Opt) -> Result<()> {
 			commit_range = Some(format!("{}..HEAD", last_tag));
 		}
 	} else if args.latest {
-		if let (Some(tag1), Some(tag2)) = (
+		if tags.len() < 2 {
+			return Err(Error::ChangelogError(String::from(
+				"latest tag cannot be processed",
+			)));
+		} else if let (Some(tag1), Some(tag2)) = (
 			tags.get_index(tags.len() - 2).map(|(k, _)| k),
 			tags.get_index(tags.len() - 1).map(|(k, _)| k),
 		) {