Remove built-in validation option

Previously, Litestream had a validator that worked most of the time
but also caused some false positives. It is difficult to provide
validation from with Litestream without controlling outside processes
that can also affect the database. As such, validation has been moved
out to the external CI test runner which provides a more consistent
validation process.

db.go

@@ -8,7 +8,6 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
-	"hash/crc64"
 	"io"
 	"io/ioutil"
 	"log"
@@ -1421,50 +1420,6 @@ func ApplyWAL(ctx context.Context, dbPath, walPath string) error {
 	return d.Close()
 }
 
-// CRC64 returns a CRC-64 ISO checksum of the database and its current position.
-//
-// This function obtains a read lock so it prevents syncs from occurring until
-// the operation is complete. The database will still be usable but it will be
-// unable to checkpoint during this time.
-//
-// If dst is set, the database file is copied to that location before checksum.
-func (db *DB) CRC64(ctx context.Context) (uint64, Pos, error) {
-	db.mu.Lock()
-	defer db.mu.Unlock()
-
-	if err := db.init(); err != nil {
-		return 0, Pos{}, err
-	} else if db.db == nil {
-		return 0, Pos{}, os.ErrNotExist
-	}
-
-	generation, err := db.CurrentGeneration()
-	if err != nil {
-		return 0, Pos{}, fmt.Errorf("cannot find current generation: %w", err)
-	} else if generation == "" {
-		return 0, Pos{}, fmt.Errorf("no current generation")
-	}
-
-	// Force a RESTART checkpoint to ensure the database is at the start of the WAL.
-	if err := db.checkpoint(ctx, generation, CheckpointModeRestart); err != nil {
-		return 0, Pos{}, err
-	}
-
-	// Obtain current position. Clear the offset since we are only reading the
-	// DB and not applying the current WAL.
-	pos := db.pos
-	pos.Offset = 0
-
-	// Seek to the beginning of the db file descriptor and checksum whole file.
-	h := crc64.New(crc64.MakeTable(crc64.ISO))
-	if _, err := db.f.Seek(0, io.SeekStart); err != nil {
-		return 0, pos, err
-	} else if _, err := io.Copy(h, db.f); err != nil {
-		return 0, pos, err
-	}
-	return h.Sum64(), pos, nil
-}
-
 // ReadWALFields iterates over the header & frames in the WAL data in r.
 // Returns salt, checksum, byte order & the last frame. WAL data must start
 // from the beginning of the WAL header and must end on either the WAL header