notifications: list all missing components when skipping nightlies

Currently when updating and skipping nightlies due to missing required
components only one such missing component is shown. Users might consider
removing the requirement for the component and updating to the specific
nightly that was missing it, only to find out that there is another, newly
discovered missing component.

With this change all required and missing components are shown when a
nightly is skipped, so users might be able to quickly identify which
nightly version, if any, has an acceptable set of missing components.

Signed-off-by: Alejandro Martinez Ruiz <amr@redhat.com>

Author: unleashed

src/dist/notifications.rs

@@ -176,8 +176,13 @@ impl<'a> Display for Notification<'a> {
             ),
             SkippingNightlyMissingComponent(components) => write!(
                 f,
-                "skipping nightly which is missing installed component '{}'",
-                components[0].short_name_in_manifest()
+                "skipping nightly which is missing installed component{} '{}'",
+                if components.len() > 1 { "s" } else { "" },
+                components
+                    .iter()
+                    .map(|component| component.short_name_in_manifest().to_owned())
+                    .collect::<Vec<_>>()
+                    .join("', '")
             ),
             ForcingUnavailableComponent(component) => {
                 write!(f, "Force-skipping unavailable component '{}'", component)