Try a new way, with testing fixtures

src/cli/mod.rs

@@ -260,6 +260,8 @@ impl FlakeHubPushCli {
         skip_all,
     )]
     pub(crate) async fn execute(self) -> color_eyre::Result<std::process::ExitCode> {
+        return Err(Error::Unauthorized("Bean salad\nLook a newline".into()))?;
+
         tracing::trace!(?self, "Executing");
         let Self {
             host,

src/error.rs

@@ -15,4 +15,12 @@ impl Error {
             Self::Unauthorized(_) | Self::Conflict { .. } => false,
         }
     }
+    pub(crate) fn maybe_github_actions_annotation(&self) {
+        if std::env::var("GITHUB_ACTIONS").is_ok() {
+            match self {
+                Error::Unauthorized(message) => println!("::error title=Unauthorized::<<EOF\n{message}\nEOF"),
+                Error::Conflict { .. } => println!("::error title=Conflict::<<EOF\n{self}\nEOF"),
+            }
+        }
+    }
 }

src/main.rs

@@ -1,3 +1,4 @@
+#![allow(unused_variables, dead_code, unreachable_code)]
 use std::{fmt::Display, io::IsTerminal};
 
 use clap::Parser;
@@ -34,7 +35,16 @@ async fn main() -> color_eyre::Result<std::process::ExitCode> {
 
     let cli = cli::FlakeHubPushCli::parse();
     cli.instrumentation.setup()?;
-    cli.execute().await
+
+    match cli.execute().await {
+        Ok(exit) => Ok(exit),
+        Err(error) => {
+            if let Some(known_error) = error.downcast_ref::<Error>() {
+                known_error.maybe_github_actions_annotation()
+            }
+            Err(error)
+        }
+    }
 }
 
 #[derive(Debug, Clone, Copy, clap::ValueEnum, serde::Serialize, serde::Deserialize)]