add a backup command

docs/changelog.txt

@@ -2,6 +2,8 @@ changelog
 
 === next
 
+++ backup command.
+
 + Option to mention all in replies.
 
 + Reduce interference between various text substitution rules.

docs/honk.8

@@ -124,6 +124,10 @@ The
 command exists to purge old data, by default 30 days.
 This removes unreferenced, unsaved posts and attachments.
 It does not remove any original content.
+.Pp
+Backups may be performed by running
+.Ic backup dirname .
+Backups only include the minimal necessary information.
 .Ss Upgrade
 Stop the old honk process.
 Backup the database.
@@ -132,10 +136,6 @@ Perform the upgrade with the
 command.
 Restart.
 .Pp
-There's also a
-.Pa blob.db
-file which is important to backup and restore.
-.Pp
 The current version of the honk binary may be printed with the
 .Ic version
 command.

honk.go

@@ -326,6 +326,13 @@ func main() {
 		}
 		name := args[1]
 		unplugserver(name)
+	case "backup":
+		if len(args) < 2 {
+			fmt.Printf("usage: honk backup dirname\n")
+			return
+		}
+		name := args[1]
+		svalbard(name)
 	case "ping":
 		if len(args) < 3 {
 			fmt.Printf("usage: honk ping from to\n")