Remove unused variables/types/functions

[staticcheck](https://staticcheck.io/) reported a number of unused
fields, functions, types, and variables across the code.

Where possible, use them (assert unchecked errors in tests, for example)
and otherwise remove them.

11 files changed, 1 insertions, 61 deletions

diff --git a/plumbing/format/packfile/fsobject.go b/plumbing/format/packfile/fsobject.go
index a395d17..238339d 100644
--- a/plumbing/format/packfile/fsobject.go
+++ b/plumbing/format/packfile/fsobject.go
@@ -13,7 +13,6 @@ import (
 // FSObject is an object from the packfile on the filesystem.
 type FSObject struct {
 	hash                 plumbing.Hash
-	h                    *ObjectHeader
 	offset               int64
 	size                 int64
 	typ                  plumbing.ObjectType
@@ -118,17 +117,3 @@ func (o *FSObject) Type() plumbing.ObjectType {
 func (o *FSObject) Writer() (io.WriteCloser, error) {
 	return nil, nil
 }
-
-type objectReader struct {
-	io.ReadCloser
-	f billy.File
-}
-
-func (r *objectReader) Close() error {
-	if err := r.ReadCloser.Close(); err != nil {
-		_ = r.f.Close()
-		return err
-	}
-
-	return r.f.Close()
-}
diff --git a/plumbing/format/packfile/packfile_test.go b/plumbing/format/packfile/packfile_test.go
index 6af8817..2eb099d 100644
--- a/plumbing/format/packfile/packfile_test.go
+++ b/plumbing/format/packfile/packfile_test.go
@@ -8,7 +8,6 @@ import (
 	"github.com/go-git/go-git/v5/plumbing"
 	"github.com/go-git/go-git/v5/plumbing/format/idxfile"
 	"github.com/go-git/go-git/v5/plumbing/format/packfile"
-	"github.com/go-git/go-git/v5/plumbing/storer"
 	. "gopkg.in/check.v1"
 )
 
@@ -236,22 +235,6 @@ var expectedHashes = []string{
 	"7e59600739c96546163833214c36459e324bad0a",
 }
 
-func assertObjects(c *C, s storer.EncodedObjectStorer, expects []string) {
-	i, err := s.IterEncodedObjects(plumbing.AnyObject)
-	c.Assert(err, IsNil)
-
-	var count int
-	err = i.ForEach(func(plumbing.EncodedObject) error { count++; return nil })
-	c.Assert(err, IsNil)
-	c.Assert(count, Equals, len(expects))
-
-	for _, exp := range expects {
-		obt, err := s.EncodedObject(plumbing.AnyObject, plumbing.NewHash(exp))
-		c.Assert(err, IsNil)
-		c.Assert(obt.Hash().String(), Equals, exp)
-	}
-}
-
 func getIndexFromIdxFile(r io.Reader) idxfile.Index {
 	idx := idxfile.NewMemoryIndex()
 	if err := idxfile.NewDecoder(r).Decode(idx); err != nil {
diff --git a/plumbing/format/packfile/parser.go b/plumbing/format/packfile/parser.go
index 4b5a570..ee5c289 100644
--- a/plumbing/format/packfile/parser.go
+++ b/plumbing/format/packfile/parser.go
@@ -46,7 +46,6 @@ type Parser struct {
 	oi         []*objectInfo
 	oiByHash   map[plumbing.Hash]*objectInfo
 	oiByOffset map[int64]*objectInfo
-	hashOffset map[plumbing.Hash]int64
 	checksum   plumbing.Hash
 
 	cache *cache.BufferLRU
diff --git a/plumbing/object/patch.go b/plumbing/object/patch.go
index 56b62c1..06bc35b 100644
--- a/plumbing/object/patch.go
+++ b/plumbing/object/patch.go
@@ -96,10 +96,6 @@ func filePatchWithContext(ctx context.Context, c *Change) (fdiff.FilePatch, erro
 
 }
 
-func filePatch(c *Change) (fdiff.FilePatch, error) {
-	return filePatchWithContext(context.Background(), c)
-}
-
 func fileContent(f *File) (content string, isBinary bool, err error) {
 	if f == nil {
 		return
diff --git a/plumbing/protocol/packp/common.go b/plumbing/protocol/packp/common.go
index ab07ac8..fef50a4 100644
--- a/plumbing/protocol/packp/common.go
+++ b/plumbing/protocol/packp/common.go
@@ -19,7 +19,6 @@ var (
 	// common
 	sp  = []byte(" ")
 	eol = []byte("\n")
-	eq  = []byte{'='}
 
 	// advertised-refs
 	null       = []byte("\x00")
diff --git a/plumbing/protocol/packp/updreq_encode.go b/plumbing/protocol/packp/updreq_encode.go
index 08a819e..1205cfa 100644
--- a/plumbing/protocol/packp/updreq_encode.go
+++ b/plumbing/protocol/packp/updreq_encode.go
@@ -9,10 +9,6 @@ import (
 	"github.com/go-git/go-git/v5/plumbing/protocol/packp/capability"
 )
 
-var (
-	zeroHashString = plumbing.ZeroHash.String()
-)
-
 // Encode writes the ReferenceUpdateRequest encoding to the stream.
 func (req *ReferenceUpdateRequest) Encode(w io.Writer) error {
 	if err := req.validate(); err != nil {
diff --git a/plumbing/protocol/packp/uppackresp.go b/plumbing/protocol/packp/uppackresp.go
index a9a7192..26ae61e 100644
--- a/plumbing/protocol/packp/uppackresp.go
+++ b/plumbing/protocol/packp/uppackresp.go
@@ -24,7 +24,6 @@ type UploadPackResponse struct {
 	r          io.ReadCloser
 	isShallow  bool
 	isMultiACK bool
-	isOk       bool
 }
 
 // NewUploadPackResponse create a new UploadPackResponse instance, the request
diff --git a/plumbing/revlist/revlist_test.go b/plumbing/revlist/revlist_test.go
index a1ee504..9f2f93b 100644
--- a/plumbing/revlist/revlist_test.go
+++ b/plumbing/revlist/revlist_test.go
@@ -55,12 +55,6 @@ func (s *RevListSuite) SetUpTest(c *C) {
 	s.Storer = sto
 }
 
-func (s *RevListSuite) commit(c *C, h plumbing.Hash) *object.Commit {
-	commit, err := object.GetCommit(s.Storer, h)
-	c.Assert(err, IsNil)
-	return commit
-}
-
 func (s *RevListSuite) TestRevListObjects_Submodules(c *C) {
 	submodules := map[string]bool{
 		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5": true,
diff --git a/plumbing/transport/client/client_test.go b/plumbing/transport/client/client_test.go
index 9ebe113..92db525 100644
--- a/plumbing/transport/client/client_test.go
+++ b/plumbing/transport/client/client_test.go
@@ -1,7 +1,6 @@
 package client
 
 import (
-	"fmt"
 	"net/http"
 	"testing"
 
@@ -68,7 +67,3 @@ func (*dummyClient) NewReceivePackSession(*transport.Endpoint, transport.AuthMet
 	transport.ReceivePackSession, error) {
 	return nil, nil
 }
-
-func typeAsString(v interface{}) string {
-	return fmt.Sprintf("%T", v)
-}
diff --git a/plumbing/transport/internal/common/common.go b/plumbing/transport/internal/common/common.go
index fdb148f..d0e9a29 100644
--- a/plumbing/transport/internal/common/common.go
+++ b/plumbing/transport/internal/common/common.go
@@ -428,11 +428,6 @@ func isRepoNotFoundError(s string) bool {
 	return false
 }
 
-var (
-	nak = []byte("NAK")
-	eol = []byte("\n")
-)
-
 // uploadPack implements the git-upload-pack protocol.
 func uploadPack(w io.WriteCloser, r io.Reader, req *packp.UploadPackRequest) error {
 	// TODO support multi_ack mode
diff --git a/plumbing/transport/ssh/common_test.go b/plumbing/transport/ssh/common_test.go
index e04a9c5..6d634d5 100644
--- a/plumbing/transport/ssh/common_test.go
+++ b/plumbing/transport/ssh/common_test.go
@@ -7,7 +7,6 @@ import (
 
 	"github.com/kevinburke/ssh_config"
 	"golang.org/x/crypto/ssh"
-	stdssh "golang.org/x/crypto/ssh"
 	. "gopkg.in/check.v1"
 )
 
@@ -99,7 +98,7 @@ func (s *SuiteCommon) TestIssue70(c *C) {
 	uploadPack.SetUpSuite(c)
 
 	config := &ssh.ClientConfig{
-		HostKeyCallback: stdssh.InsecureIgnoreHostKey(),
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
 	}
 	r := &runner{
 		config: config,