skopeo: add a helper method for inspecting a container image

This is basically the same thing as in podman.rs, just for skopeo (and without
escaping the mount namespace).

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

lib/src/lib.rs

@@ -42,6 +42,8 @@ mod k8sapitypes;
 pub(crate) mod mount;
 #[cfg(feature = "install")]
 mod podman;
+#[cfg(feature = "install")]
+mod skopeo;
 pub mod spec;
 
 #[cfg(feature = "docgen")]

lib/src/skopeo.rs

@@ -0,0 +1,22 @@
+use std::process::Command;
+use anyhow::Result;
+use serde::Deserialize;
+
+#[derive(Deserialize)]
+#[serde(rename_all = "PascalCase")]
+pub(crate) struct Inspect {
+    pub(crate) digest: String,
+}
+
+/// Given an image ID, return its manifest digest
+pub(crate) fn oci_archive_digest(imageref: &str) -> Result<String> {
+    let o = Command::new("skopeo")
+        .args(["inspect", imageref])
+        .output().expect("running skopeo");
+    let st = o.status;
+    if !st.success() {
+        anyhow::bail!("Failed to execute skopeo inspect: {st:?}");
+    }
+    let i: Inspect = serde_json::from_slice(&o.stdout)?;
+    Ok(i.digest)
+}