*: Small fixes to remove linter warnings

Signed-off-by: Paulo Gomes <[e-mail]>

plumbing/format/index/decoder.go

···
 		peeked, err = d.buf.Peek(peekLen)
 		if len(peeked) < peekLen {
 			// there can't be an extension at this point, so let's bail out
-			err = nil
 			break
 		}
 		if err != nil {

repository.go

···
 	return r.Storer.SetConfig(cfg)
 }
 
-func (r *Repository) updateRemoteConfigIfNeeded(o *CloneOptions, c *config.RemoteConfig, head *plumbing.Reference) error {
+func (r *Repository) updateRemoteConfigIfNeeded(o *CloneOptions, c *config.RemoteConfig, _ *plumbing.Reference) error {
 	if !o.SingleBranch {
 		return nil
 	}

storage/filesystem/dotgit/dotgit_test.go

···
 	testObjectsWithPrefix(c, fs, dir)
 }
 
-func testObjects(c *C, fs billy.Filesystem, dir *DotGit) {
+func testObjects(c *C, _ billy.Filesystem, dir *DotGit) {
 	hashes, err := dir.Objects()
 	c.Assert(err, IsNil)
 	c.Assert(hashes, HasLen, 187)
···
 	c.Assert(hashes[2].String(), Equals, "03db8e1fbe133a480f2867aac478fd866686d69e")
 }
 
-func testObjectsWithPrefix(c *C, fs billy.Filesystem, dir *DotGit) {
+func testObjectsWithPrefix(c *C, _ billy.Filesystem, dir *DotGit) {
 	prefix, _ := hex.DecodeString("01d5")
 	hashes, err := dir.ObjectsWithPrefix(prefix)
 	c.Assert(err, IsNil)

worktree_linux.go

···
+//go:build linux
 // +build linux
 
 package git
···
 	}
 }
 
-func isSymlinkWindowsNonAdmin(err error) bool {
+func isSymlinkWindowsNonAdmin(_ error) bool {
 	return false
 }

worktree_status.go

···
 	return w.r.Storer.SetEncodedObject(obj)
 }
 
-func (w *Worktree) fillEncodedObjectFromFile(dst io.Writer, path string, fi os.FileInfo) (err error) {
+func (w *Worktree) fillEncodedObjectFromFile(dst io.Writer, path string, _ os.FileInfo) (err error) {
 	src, err := w.Filesystem.Open(path)
 	if err != nil {
 		return err
···
 	return err
 }
 
-func (w *Worktree) fillEncodedObjectFromSymlink(dst io.Writer, path string, fi os.FileInfo) error {
+func (w *Worktree) fillEncodedObjectFromSymlink(dst io.Writer, path string, _ os.FileInfo) error {
 	target, err := w.Filesystem.Readlink(path)
 	if err != nil {
 		return err