feat: Add the vantagectl backup and inspect subcommands

Progress output goes to stderr so --out - stays a clean pipe into restic,
age or aws s3 cp. Archive names carry no colon, because these get copied
onto Windows shares.

internal/cmd/inspect.go

@@ -1,7 +1,78 @@
 package cmd
 
-import "github.com/spf13/cobra"
+import (
+	"fmt"
+	"io"
+	"strings"
+	"text/tabwriter"
+
+	"gitea.hostxtra.co.uk/mrhid6/vantage/shared/backup"
+	"github.com/spf13/cobra"
+)
 
 func newInspectCmd() *cobra.Command {
-	return &cobra.Command{Use: "inspect ARCHIVE", Short: "Print an archive's manifest"}
+	return &cobra.Command{
+		Use:   "inspect ARCHIVE",
+		Short: "Print an archive's manifest",
+		Long: "inspect reads an archive and prints what it holds. It contacts no\n" +
+			"database, so it is safe to run against an archive of unknown origin\n" +
+			"and is the fastest way to find out whether one is worth anything.",
+		Args: cobra.ExactArgs(1),
+		RunE: func(c *cobra.Command, args []string) error {
+			archive, err := backup.Open(args[0])
+			if err != nil {
+				return err
+			}
+			defer archive.Close()
+			renderManifest(c.OutOrStdout(), archive.Manifest())
+			return nil
+		},
+	}
+}
+
+// renderManifest prints a manifest for a human.
+func renderManifest(w io.Writer, m backup.Manifest) {
+	fmt.Fprintf(w, "Created       %s\n", m.CreatedAt.UTC().Format("2006-01-02 15:04:05 MST"))
+	fmt.Fprintf(w, "Database      %s\n", m.MongoDB)
+	fmt.Fprintf(w, "MongoDB       %s\n", m.MongoServerVersion)
+	fmt.Fprintf(w, "Written by    vantagectl %s on %s\n", m.VantageVersion, m.Hostname)
+	fmt.Fprintf(w, "Format        version %d\n", m.FormatVersion)
+
+	if m.KeyFingerprint == nil {
+		fmt.Fprintf(w, "Key           none recorded — this archive cannot be checked "+
+			"against any KEY_ENCRYPTION_KEY\n")
+	} else {
+		fmt.Fprintf(w, "Key           %s\n", *m.KeyFingerprint)
+	}
+	if len(m.Excluded) > 0 {
+		fmt.Fprintf(w, "Excluded      %s\n", strings.Join(m.Excluded, ", "))
+	}
+
+	var docs, bytes int64
+	for _, c := range m.Collections {
+		docs += c.Documents
+		bytes += c.Bytes
+	}
+	fmt.Fprintf(w, "\n%d collections, %d documents, %s\n\n",
+		len(m.Collections), docs, humanBytes(bytes))
+
+	tw := tabwriter.NewWriter(w, 0, 0, 2, ' ', 0)
+	fmt.Fprintln(tw, "COLLECTION\tDOCUMENTS\tSIZE")
+	for _, c := range m.Collections {
+		fmt.Fprintf(tw, "%s\t%d\t%s\n", c.Name, c.Documents, humanBytes(c.Bytes))
+	}
+	tw.Flush()
+}
+
+func humanBytes(n int64) string {
+	const unit = 1024
+	if n < unit {
+		return fmt.Sprintf("%d B", n)
+	}
+	div, exp := int64(unit), 0
+	for v := n / unit; v >= unit; v /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf("%.1f %cB", float64(n)/float64(div), "KMGTP"[exp])
 }