internal/pkg: expose status file

This is useful for external tooling.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg.go

@@ -1790,6 +1790,18 @@ func (pending *pendingArtifactDep) cure(c *Cache) {
 	pending.errsMu.Unlock()
 }
 
+// OpenStatus attempts to open the status file associated to an [Artifact]. If
+// err is nil, the caller must close the resulting reader.
+func (c *Cache) OpenStatus(a Artifact) (r io.ReadSeekCloser, err error) {
+	c.identMu.RLock()
+	r, err = os.Open(c.base.Append(
+		dirStatus,
+		Encode(c.Ident(a).Value())).String(),
+	)
+	c.identMu.RUnlock()
+	return
+}
+
 // Close cancels all pending cures and waits for them to clean up.
 func (c *Cache) Close() {
 	c.closeOnce.Do(func() {