tool: always include version in PRETTY_NAME

... to give a consistent user experience in systemd-boot.

Fixes #220.

rust/tool/shared/src/generation.rs

@@ -67,7 +67,16 @@ impl Generation {
         }
     }
 
-    /// Describe the generation in a single line.
+    /// A helper for describe functions below.
+    fn describe_specialisation(&self) -> String {
+        if let Some(specialization) = &self.specialisation_name {
+            format!("-{specialization}")
+        } else {
+            "".to_string()
+        }
+    }
+
+    /// Describe the generation in a single line for humans.
     ///
     /// Emulates how NixOS's current systemd-boot-builder.py describes generations so that the user
     /// interface remains similar.
@@ -83,14 +92,15 @@ impl Generation {
         format!(
             "Generation {}{}, {}",
             self.version,
-            if let Some(specialization) = &self.specialisation_name {
-                format!("-{specialization}")
-            } else {
-                "".to_string()
-            },
+            self.describe_specialisation(),
             build_time
         )
     }
+
+    /// A unique short identifier.
+    pub fn version_tag(&self) -> String {
+        format!("{}{}", self.version, self.describe_specialisation(),)
+    }
 }
 
 impl fmt::Display for Generation {

rust/tool/shared/src/os_release.rs

@@ -26,10 +26,21 @@ impl OsRelease {
         // Because the ID field here does not have the same meaning as in a real os-release file,
         // it is fine to use a dummy value.
         map.insert("ID".into(), String::from("lanza"));
+
+        // systemd-boot will only show VERSION_ID when PRETTY_NAME is not unique. This is
+        // confusing to users. Make sure that our PRETTY_NAME is unique, so we get a consistent
+        // user experience.
+        //
+        // See #220.
         map.insert(
             "PRETTY_NAME".into(),
-            generation.spec.bootspec.bootspec.label.clone(),
+            format!(
+                "{} ({})",
+                generation.spec.bootspec.bootspec.label,
+                generation.describe()
+            ),
         );
+
         map.insert("VERSION_ID".into(), generation.describe());
 
         Ok(Self(map))

rust/tool/systemd/tests/os_release.rs

@@ -27,8 +27,8 @@ fn generate_expected_os_release() -> Result<()> {
 
     let expected = expect![[r#"
         ID=lanza
-        PRETTY_NAME=LanzaOS
-        VERSION_ID=Generation 1, Built on 1970-01-01
+        PRETTY_NAME=LanzaOS (Generation 1, 1970-01-01)
+        VERSION_ID=Generation 1, 1970-01-01
     "#]];
 
     expected.assert_eq(&String::from_utf8(os_release_section)?);