build: replace the deprecated golint linter with revive

This fixes up a small number of new lint items also

.golangci.yml

@@ -5,7 +5,7 @@ linters:
     - deadcode
     - errcheck
     - goimports
-    - golint
+    - revive
     - ineffassign
     - structcheck
     - varcheck

backend/compress/compress.go

@@ -1260,7 +1260,7 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (rc io.Read
 		return o.Object.Open(ctx, options...)
 	}
 	// Get offset and limit from OpenOptions, pass the rest to the underlying remote
-	var openOptions []fs.OpenOption = []fs.OpenOption{&fs.SeekOption{Offset: 0}}
+	var openOptions = []fs.OpenOption{&fs.SeekOption{Offset: 0}}
 	var offset, limit int64 = 0, -1
 	for _, option := range options {
 		switch x := option.(type) {

backend/tardigrade/object.go

@@ -132,7 +132,7 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (_ io.ReadC
 	// Convert the semantics of HTTP range headers to an offset and length
 	// that libuplink can use.
 	var (
-		offset int64 = 0
+		offset int64
 		length int64 = -1
 	)
 

backend/uptobox/uptobox.go

@@ -304,7 +304,7 @@ func (f *Fs) List(ctx context.Context, dir string) (entries fs.DirEntries, err e
 
 	var limit uint64 = 100 // max number of objects per request - 100 seems to be the maximum the api accepts
 	var page uint64 = 1
-	var offset uint64 = 0 // for the next page of requests
+	var offset uint64 // for the next page of requests
 
 	for {
 		opts := &api.MetadataRequestOptions{

cmd/selfupdate/help.go

@@ -4,7 +4,7 @@
 package selfupdate
 
 // Note: "|" will be replaced by backticks in the help string below
-var selfUpdateHelp string = `
+var selfUpdateHelp = `
 This command downloads the latest release of rclone and replaces
 the currently running binary. The download is verified with a hashsum
 and cryptographically signed signature.

lib/http/http.go

@@ -124,7 +124,7 @@ func NewServer(listeners, tlsListeners []net.Listener, opt Options) (Server, err
 	}
 
 	// Prepare TLS config
-	var tlsConfig *tls.Config = nil
+	var tlsConfig *tls.Config
 
 	useSSL := useSSL(opt)
 	if (opt.SslCert != "") != useSSL {

vfs/vfs.go

@@ -566,7 +566,7 @@ func (vfs *VFS) Statfs() (total, used, free int64) {
 			vfs.usage, err = doAbout(ctx)
 		}
 		if vfs.Opt.UsedIsSize {
-			var usedBySizeAlgorithm int64 = 0
+			var usedBySizeAlgorithm int64
 			// Algorithm from `rclone size`
 			err = walk.ListR(ctx, vfs.f, "", true, -1, walk.ListObjects, func(entries fs.DirEntries) error {
 				entries.ForObject(func(o fs.Object) {