fix go vet issues, add go vet to CI

.travis.yml

@@ -42,6 +42,7 @@ script:
   - export PATH=$GIT_DIST_PATH:$PATH
   - git version
   - make test-coverage
+  - go vet ./...
 
 after_success:
   - bash <(curl -s https://codecov.io/bash)

plumbing/format/packfile/decoder.go

@@ -310,13 +310,13 @@ func (d *Decoder) DecodeObjectAt(offset int64) (plumbing.EncodedObject, error) {
 		return nil, ErrNonSeekable
 	}
 
-	beforeJump, err := d.s.Seek(offset)
+	beforeJump, err := d.s.SeekFromStart(offset)
 	if err != nil {
 		return nil, err
 	}
 
 	defer func() {
-		_, seekErr := d.s.Seek(beforeJump)
+		_, seekErr := d.s.SeekFromStart(beforeJump)
 		if err == nil {
 			err = seekErr
 		}

plumbing/format/packfile/scanner.go

@@ -300,8 +300,9 @@ func (s *Scanner) copyObject(w io.Writer) (int64, error) {
 	return io.Copy(w, s.zr)
 }
 
-// Seek sets a new offset from start, returns the old position before the change
-func (s *Scanner) Seek(offset int64) (previous int64, err error) {
+// SeekFromStart sets a new offset from start, returns the old position before
+// the change.
+func (s *Scanner) SeekFromStart(offset int64) (previous int64, err error) {
 	// if seeking we assume that you are not interested on the header
 	if s.version == 0 {
 		s.version = VersionSupported

plumbing/format/packfile/scanner_test.go

@@ -4,9 +4,10 @@ import (
 	"bytes"
 	"io"
 
-	. "gopkg.in/check.v1"
-	"github.com/src-d/go-git-fixtures"
 	"gopkg.in/src-d/go-git.v4/plumbing"
+
+	"github.com/src-d/go-git-fixtures"
+	. "gopkg.in/check.v1"
 )
 
 type ScannerSuite struct {

plumbing/format/pktline/scanner_test.go

@@ -218,7 +218,7 @@ func ExampleScanner() {
 	for s.Scan() {
 		payload := s.Bytes()
 		if len(payload) == 0 { // zero sized payloads correspond to flush-pkts.
-			fmt.Println("FLUSH-PKT DETECTED\n")
+			fmt.Println("FLUSH-PKT DETECTED")
 		} else { // otherwise, you will be able to access the full payload.
 			fmt.Printf("PAYLOAD = %q\n", string(payload))
 		}

plumbing/object/change_adaptor.go

@@ -1,6 +1,7 @@
 package object
 
 import (
+	"errors"
 	"fmt"
 
 	"gopkg.in/src-d/go-git.v4/utils/merkletrie"
@@ -15,11 +16,11 @@ func newChange(c merkletrie.Change) (*Change, error) {
 
 	var err error
 	if ret.From, err = newChangeEntry(c.From); err != nil {
-		return nil, fmt.Errorf("From field: ", err)
+		return nil, fmt.Errorf("From field: %s", err)
 	}
 
 	if ret.To, err = newChangeEntry(c.To); err != nil {
-		return nil, fmt.Errorf("To field: ", err)
+		return nil, fmt.Errorf("To field: %s", err)
 	}
 
 	return ret, nil
@@ -32,7 +33,7 @@ func newChangeEntry(p noder.Path) (ChangeEntry, error) {
 
 	asTreeNoder, ok := p.Last().(*treeNoder)
 	if !ok {
-		return ChangeEntry{}, fmt.Errorf("cannot transform non-TreeNoders")
+		return ChangeEntry{}, errors.New("cannot transform non-TreeNoders")
 	}
 
 	return ChangeEntry{
@@ -52,7 +53,7 @@ func newChanges(src merkletrie.Changes) (Changes, error) {
 	for i, e := range src {
 		ret[i], err = newChange(e)
 		if err != nil {
-			return nil, fmt.Errorf("change #%d: %s", err)
+			return nil, fmt.Errorf("change #%d: %s", i, err)
 		}
 	}
 

plumbing/object/change_test.go

@@ -236,10 +236,7 @@ func (s *ChangeSuite) TestNoFileFilemodes(c *C) {
 		c.Assert(err, IsNil)
 		for _, change := range changes {
 			_, _, err := change.Files()
-			if err != nil {
-				panic(err)
-				c.Assert(err, IsNil)
-			}
+			c.Assert(err, IsNil)
 		}
 
 		prev = commit

remote.go

@@ -41,7 +41,7 @@ func (r *Remote) String() string {
 	fetch := r.c.URL
 	push := r.c.URL
 
-	return fmt.Sprintf("%s\t%s (fetch)\n%[1]s\t%s (push)", r.c.Name, fetch, push)
+	return fmt.Sprintf("%s\t%s (fetch)\n%[1]s\t%[3]s (push)", r.c.Name, fetch, push)
 }
 
 // Fetch fetches references from the remote to the local repository.

utils/merkletrie/difftree_test.go

@@ -120,7 +120,7 @@ func newChanges(original merkletrie.Changes) (changes, error) {
 				path:   c.From.String(),
 			}
 		default:
-			panic(fmt.Sprintf("unsupported action %d", c.Action))
+			panic(fmt.Sprintf("unsupported action %d", action))
 		}
 	}
 

utils/merkletrie/internal/fsnoder/new.go

@@ -34,7 +34,7 @@ func decodeDir(data []byte, isRoot bool) (*dir, error) {
 	var name string
 	switch end := bytes.IndexRune(data, dirStartMark); end {
 	case -1:
-		return nil, fmt.Errorf("%c not found")
+		return nil, fmt.Errorf("%c not found", dirStartMark)
 	case 0:
 		if isRoot {
 			name = ""

utils/merkletrie/iter_test.go

@@ -65,7 +65,7 @@ func (t test) run(c *C, iter *merkletrie.Iter,
 
 	var obtained noder.Path
 	var err error
-	for i := range t.operations {
+	for i, b := range t.operations {
 		comment := Commentf("\ntree: %q\ntest #%d (%q)\noperation #%d (%q)",
 			treeDescription, testNumber, t.operations, i, t.operations[i])
 
@@ -81,8 +81,8 @@ func (t test) run(c *C, iter *merkletrie.Iter,
 				c.Assert(err, IsNil)
 			}
 		default:
-			c.Fatalf("unknown operation at test %d, operation %d (%s)\n",
-				testNumber, i, t.operations[i])
+			c.Fatalf("unknown operation at test %d, operation %d (%c)\n",
+				testNumber, i, b)
 		}
 		if i >= len(expectedChunks) {
 			c.Assert(err, Equals, io.EOF, comment)