Add example script for restoring a backup

This was originally contributed by @codygman and edited by me to adopt newer
`turtle` idioms

examples/restoreBackup.hs

@@ -0,0 +1,47 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+import Turtle
+
+import qualified Control.Foldl as Fold
+
+main = do
+  -- Backup the old database
+  inproc "mysqldump" ["-uroot", "myproject"] empty
+      & output "revert.sql"
+
+  let serverName = "lalala"
+  let backupDir  = "/backups/db/myproject/"
+
+  -- Obtain newest filename from server
+  let query :: Shell Line
+      query = inproc "ssh"
+          [ serverName
+          , format ("ls -Art "%fp%" | tail -n 1") backupDir
+          ]
+          empty
+  result <- fold query Fold.head
+  newestFileName <- case result of
+      Nothing   -> die "Couldn't get backup path"
+      Just text -> return (fromText (lineToText text))
+
+  let backupFilePath = backupDir </> newestFileName
+  let localFilePath  = "/tmp/" </> newestFileName
+
+  -- Download the backup
+  procs "rsync"
+      [ "-avcz"
+      , format (s%":"%fp) serverName backupFilePath
+      , format fp localFilePath
+      ]
+      empty
+
+  let dbName = "myproject-copy"
+
+  -- Drop the old database
+  shells ("mysqladmin -uroot drop -f " <> dbName) empty
+
+  -- Restore the database from the downloaded backup
+  inproc "zcat" [format fp localFilePath] empty
+      & procs "mysql" ["-uroot", dbName]
+
+  echo "Backup restored"