install: make the source digest optional

This is a prep work for the following commit. It will implement pulling
the container image from an explicitly given container reference. Thus,
there's no need to always fetch the digest because the caller is being
explicit about the container image, so let's make the field optional.

Signed-off-by: Ondřej Budai <[email protected]>

Author: ondrejbudai

lib/src/install.rs

@@ -222,7 +222,7 @@ pub(crate) struct SourceInfo {
     /// Image reference we'll pull from (today always containers-storage: type)
     pub(crate) imageref: ostree_container::ImageReference,
     /// The digest to use for pulls
-    pub(crate) digest: String,
+    pub(crate) digest: Option<String>,
     /// Whether or not SELinux appears to be enabled in the source commit
     pub(crate) selinux: bool,
 }
@@ -384,7 +384,7 @@ impl SourceInfo {
         let selinux = crate::lsm::xattrs_have_selinux(&xattrs);
         Ok(Self {
             imageref,
-            digest,
+            digest: Some(digest),
             selinux,
         })
     }
@@ -572,8 +572,12 @@ async fn initialize_ostree_root_from_self(
     let mut temporary_dir = None;
     let src_imageref = if state.skopeo_supports_containers_storage {
         // We always use exactly the digest of the running image to ensure predictability.
-        let spec =
-            crate::utils::digested_pullspec(&state.source.imageref.name, &state.source.digest);
+        let digest = state
+            .source
+            .digest
+            .as_ref()
+            .ok_or_else(|| anyhow::anyhow!("Missing container image digest"))?;
+        let spec = crate::utils::digested_pullspec(&state.source.imageref.name, digest);
         ostree_container::ImageReference {
             transport: ostree_container::Transport::ContainerStorage,
             name: spec,