✨ Stop if there is no tags in repo and release option is absent

src/changelog.rs

@@ -1,9 +1,11 @@
 use std::path::Path;
+use std::result::Result;
 
 use git2::Repository;
 use handlebars::Handlebars;
 
 use crate::commit::Commit;
+use crate::error::Error;
 use crate::version::Version;
 
 const TEMPLATE: &str = "{{#each versions as |version|}}
@@ -89,11 +91,17 @@ impl Changelog {
         Changelog { versions }
     }
 
-    pub fn to_markdown(&self, release: Option<&str>, print_authors: bool) -> String {
+    pub fn to_markdown(&self, release: Option<&str>, print_authors: bool) -> Result<String, Error> {
         let mut versions = self.versions.clone();
 
         match release {
             None => {
+                if let Some(version) = versions.first() {
+                    if version.name == "HEAD" {
+                        return Err(Error::NoTag);
+                    }
+                }
+
                 if !versions.is_empty() {
                     versions.remove(0);
                 }
@@ -116,6 +124,6 @@ impl Changelog {
             },
         });
 
-        reg.render_template(TEMPLATE, &json).unwrap()
+        Ok(reg.render_template(TEMPLATE, &json).unwrap())
     }
 }

src/error.rs

@@ -0,0 +1,27 @@
+use std::error;
+use std::fmt;
+
+#[derive(Debug, Clone)]
+pub enum Error {
+    NoTag,
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Error::NoTag => write!(f, "Your repository does not seem to contain any tag. Please use the release option if you wish to generate a changelog either way.")
+        }
+    }
+}
+
+impl error::Error for Error {
+    fn description(&self) -> &str {
+        match *self {
+            Error::NoTag => "Your repository does not seem to contain any tag. Please use the release option if you wish to generate a changelog either way."
+        }
+    }
+
+    fn cause(&self) -> Option<&error::Error> {
+        None
+    }
+}

src/lib.rs

@@ -7,10 +7,12 @@ extern crate lazy_static;
 
 mod changelog;
 mod commit;
+mod error;
 mod group;
 mod version;
 
 pub use crate::changelog::Changelog;
 pub use crate::commit::Commit;
+pub use crate::error::Error;
 pub use crate::group::Group;
 pub use crate::version::Version;

src/main.rs

@@ -9,12 +9,14 @@ extern crate clap;
 
 use std::fs::{self, File};
 use std::io::prelude::*;
+use std::process;
 
 use regex::Regex;
 
 mod changelog;
 mod cli;
 mod commit;
+mod error;
 mod group;
 mod version;
 
@@ -35,10 +37,16 @@ fn main() {
     let get_delta = |from| {
         let changelog = Changelog::from(repository, from);
 
-        changelog.to_markdown(
+        match changelog.to_markdown(
             matches.value_of("release"),
             matches.is_present("print-authors"),
-        )
+        ) {
+            Err(error) => {
+                eprintln!("{}", error);
+                process::exit(1);
+            }
+            Ok(delta) => delta,
+        }
     };
 
     let format = |header, delta, footer| {