Add cache

This commits adds rudimentary support for a cache directory, enabled by
default. The cache directory is created if it does not exist. The cache
is used if there's anything in it, newly created snapshot and index
files are written to the cache automatically.

cmd/restic/global.go

@@ -19,6 +19,7 @@ import (
 	"github.com/restic/restic/internal/backend/s3"
 	"github.com/restic/restic/internal/backend/sftp"
 	"github.com/restic/restic/internal/backend/swift"
+	"github.com/restic/restic/internal/cache"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/options"
 	"github.com/restic/restic/internal/repository"
@@ -38,6 +39,8 @@ type GlobalOptions struct {
 	Quiet        bool
 	NoLock       bool
 	JSON         bool
+	CacheDir     string
+	NoCache      bool
 
 	ctx      context.Context
 	password string
@@ -68,7 +71,8 @@ func init() {
 	f.BoolVarP(&globalOptions.Quiet, "quiet", "q", false, "do not output comprehensive progress report")
 	f.BoolVar(&globalOptions.NoLock, "no-lock", false, "do not lock the repo, this allows some operations on read-only repos")
 	f.BoolVarP(&globalOptions.JSON, "json", "", false, "set output mode to JSON for commands that support it")
-
+	f.StringVar(&globalOptions.CacheDir, "cache-dir", "", "set the cache directory")
+	f.BoolVar(&globalOptions.NoCache, "no-cache", false, "do not use a local cache")
 	f.StringSliceVarP(&globalOptions.Options, "option", "o", []string{}, "set extended option (`key=value`, can be specified multiple times)")
 
 	restoreTerminal()
@@ -322,6 +326,17 @@ func OpenRepository(opts GlobalOptions) (*repository.Repository, error) {
 		return nil, err
 	}
 
+	if opts.NoCache {
+		return s, nil
+	}
+
+	cache, err := cache.New(s.Config().ID, opts.CacheDir)
+	if err != nil {
+		Warnf("unable to open cache: %v\n", err)
+	} else {
+		s.UseCache(cache)
+	}
+
 	return s, nil
 }
 

cmd/restic/integration_helpers_test.go

@@ -199,6 +199,7 @@ func withTestEnvironment(t testing.TB) (env *testEnvironment, cleanup func()) {
 	env.gopts = GlobalOptions{
 		Repo:     env.repo,
 		Quiet:    true,
+		CacheDir: env.cache,
 		ctx:      context.Background(),
 		password: TestPassword,
 		stdout:   os.Stdout,