Clarify remote-only update checks

src/bin/dosh-client.rs

@@ -4548,27 +4548,36 @@ fn run_update(
             }
             None => println!("latest: unknown"),
         }
-        if let Some(latest_url) =
-            local_installer_role.and_then(|_| latest_release_download_url(&repo, &artifact))
-        {
-            let mut status = "missing";
-            let mut display_url = latest_url.clone();
-            if let Some(tag_url) =
-                effective_update_artifact_tag(local_version, latest_tag.as_deref())
-                    .as_deref()
-                    .and_then(|tag| release_tag_download_url(&repo, tag, &artifact))
-            {
-                display_url = tag_url;
-                if url_reachable(&display_url)? {
+        match local_prebuilt_check_target(
+            local_installer_role,
+            update_remote_server,
+            &repo,
+            &artifact,
+        ) {
+            LocalPrebuiltCheckTarget::Url(latest_url) => {
+                let mut status = "missing";
+                let mut display_url = latest_url.clone();
+                if let Some(tag_url) =
+                    effective_update_artifact_tag(local_version, latest_tag.as_deref())
+                        .as_deref()
+                        .and_then(|tag| release_tag_download_url(&repo, tag, &artifact))
+                {
+                    display_url = tag_url;
+                    if url_reachable(&display_url)? {
+                        status = "available";
+                    }
+                } else if url_reachable(&latest_url)? {
                     status = "available";
                 }
-            } else if url_reachable(&latest_url)? {
-                status = "available";
+                println!("prebuilt: {status} ({artifact})");
+                println!("prebuilt_url: {display_url}");
+            }
+            LocalPrebuiltCheckTarget::NonHttpRepo => {
+                println!("prebuilt: unavailable for non-HTTP repo");
+            }
+            LocalPrebuiltCheckTarget::RemoteOnly => {
+                println!("prebuilt: skipped for remote-only update");
             }
-            println!("prebuilt: {status} ({artifact})");
-            println!("prebuilt_url: {display_url}");
-        } else {
-            println!("prebuilt: unavailable for non-HTTP repo");
         }
         return Ok(());
     }
@@ -4605,6 +4614,31 @@ fn run_update(
     Ok(())
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+enum LocalPrebuiltCheckTarget {
+    Url(String),
+    NonHttpRepo,
+    RemoteOnly,
+}
+
+fn local_prebuilt_check_target(
+    local_installer_role: Option<&str>,
+    update_remote_server: bool,
+    repo: &str,
+    artifact: &str,
+) -> LocalPrebuiltCheckTarget {
+    if local_installer_role.is_none() {
+        return if update_remote_server {
+            LocalPrebuiltCheckTarget::RemoteOnly
+        } else {
+            LocalPrebuiltCheckTarget::NonHttpRepo
+        };
+    }
+    latest_release_download_url(repo, artifact)
+        .map(LocalPrebuiltCheckTarget::Url)
+        .unwrap_or(LocalPrebuiltCheckTarget::NonHttpRepo)
+}
+
 fn run_update_installer(
     config: &dosh::config::ClientConfig,
     repo: &str,
@@ -13139,6 +13173,40 @@ mod tests {
         assert!(!UpdateRole::Both.updates_remote_server_from_os("linux"));
     }
 
+    #[test]
+    fn update_check_distinguishes_remote_only_from_missing_local_prebuilt() {
+        assert_eq!(
+            super::local_prebuilt_check_target(
+                Some("client"),
+                false,
+                "https://git.palav.dev/Palav/dosh.git",
+                "dosh-windows-x86_64.zip",
+            ),
+            super::LocalPrebuiltCheckTarget::Url(
+                "https://git.palav.dev/Palav/dosh/releases/latest/download/dosh-windows-x86_64.zip"
+                    .to_string()
+            )
+        );
+        assert_eq!(
+            super::local_prebuilt_check_target(
+                Some("client"),
+                false,
+                "git@git.palav.dev:Palav/dosh.git",
+                "dosh-windows-x86_64.zip",
+            ),
+            super::LocalPrebuiltCheckTarget::NonHttpRepo
+        );
+        assert_eq!(
+            super::local_prebuilt_check_target(
+                UpdateRole::Server.local_installer_arg_for_os("windows"),
+                UpdateRole::Server.updates_remote_server_from_os("windows"),
+                "https://git.palav.dev/Palav/dosh.git",
+                "dosh-windows-x86_64.zip",
+            ),
+            super::LocalPrebuiltCheckTarget::RemoteOnly
+        );
+    }
+
     #[test]
     fn update_scripts_are_native_to_the_platform() {
         let config = ClientConfig {