cmd/mbf: preset status command

This exposes the new OpenStatus cache method.

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

cmd/mbf/main.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"io"
 	"log"
 	"os"
 	"os/signal"
@@ -260,6 +261,30 @@ func main() {
 			)
 	}
 
+	c.NewCommand(
+		"status",
+		"Display the status file of an artifact",
+		func(args []string) error {
+			if len(args) != 1 {
+				return errors.New("status requires 1 argument")
+			}
+			if p, ok := rosa.ResolveName(args[0]); !ok {
+				return fmt.Errorf("unknown artifact %q", args[0])
+			} else {
+				r, err := cache.OpenStatus(rosa.Std.Load(p))
+				if err != nil {
+					if errors.Is(err, os.ErrNotExist) {
+						return errors.New(args[0] + " was never cured")
+					}
+					return err
+				}
+
+				_, err = io.Copy(os.Stdout, r)
+				return errors.Join(err, r.Close())
+			}
+		},
+	)
+
 	{
 		var (
 			flagNet     bool

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() {