diff --git a/blob.go b/blob.go
index 478682e..10b8ea4 100644
--- a/blob.go
+++ b/blob.go
@@ -25,6 +25,7 @@ func (b *Blob) Data() (io.Reader, error) {
 	return bytes.NewBuffer(stdout), nil
 }
 
+// DataPipeline gets content of blob and write the result or error to stdout or stderr
 func (b *Blob) DataPipeline(stdout, stderr io.Writer) error {
 	return NewCommand("show", b.ID.String()).RunInDirPipeline(b.repo.Path, stdout, stderr)
 }
diff --git a/command.go b/command.go
index f7fce67..ab42ea3 100644
--- a/command.go
+++ b/command.go
@@ -40,13 +40,11 @@ func (c *Command) AddArguments(args ...string) *Command {
 	return c
 }
 
-const DEFAULT_TIMEOUT = 60 * time.Second
-
 // RunInDirTimeoutPipeline executes the command in given directory with given timeout,
 // it pipes stdout and stderr to given io.Writer.
 func (c *Command) RunInDirTimeoutPipeline(timeout time.Duration, dir string, stdout, stderr io.Writer) error {
 	if timeout == -1 {
-		timeout = DEFAULT_TIMEOUT
+		timeout = 60 * time.Second
 	}
 
 	if len(dir) == 0 {
@@ -106,7 +104,7 @@ func (c *Command) RunInDirPipeline(dir string, stdout, stderr io.Writer) error {
 	return c.RunInDirTimeoutPipeline(-1, dir, stdout, stderr)
 }
 
-// RunInDir executes the command in given directory
+// RunInDirBytes executes the command in given directory
 // and returns stdout in []byte and error (combined with stderr).
 func (c *Command) RunInDirBytes(dir string) ([]byte, error) {
 	return c.RunInDirTimeout(-1, dir)
diff --git a/commit.go b/commit.go
index e16246f..dc5f2bd 100644
--- a/commit.go
+++ b/commit.go
@@ -18,13 +18,13 @@ import (
 // Commit represents a git commit.
 type Commit struct {
 	Tree
-	ID            sha1 // The ID of this commit object
+	ID            SHA1 // The ID of this commit object
 	Author        *Signature
 	Committer     *Signature
 	CommitMessage string
 
-	parents        []sha1 // SHA1 strings
-	submoduleCache *objectCache
+	parents        []SHA1 // SHA1 strings
+	submoduleCache *ObjectCache
 }
 
 // Message returns the commit message. Same as retrieving CommitMessage directly.
@@ -39,9 +39,9 @@ func (c *Commit) Summary() string {
 
 // ParentID returns oid of n-th parent (0-based index).
 // It returns nil if no such parent exists.
-func (c *Commit) ParentID(n int) (sha1, error) {
+func (c *Commit) ParentID(n int) (SHA1, error) {
 	if n >= len(c.parents) {
-		return sha1{}, ErrNotExist{"", ""}
+		return SHA1{}, ErrNotExist{"", ""}
 	}
 	return c.parents[n], nil
 }
@@ -73,6 +73,7 @@ func isImageFile(data []byte) (string, bool) {
 	return contentType, false
 }
 
+// IsImageFile is a file image type
 func (c *Commit) IsImageFile(name string) bool {
 	blob, err := c.GetBlobByPath(name)
 	if err != nil {
@@ -95,7 +96,7 @@ func (c *Commit) GetCommitByPath(relpath string) (*Commit, error) {
 	return c.repo.getCommitByPathWithID(c.ID, relpath)
 }
 
-// AddAllChanges marks local changes to be ready for commit.
+// AddChanges marks local changes to be ready for commit.
 func AddChanges(repoPath string, all bool, files ...string) error {
 	cmd := NewCommand("add")
 	if all {
@@ -105,6 +106,7 @@ func AddChanges(repoPath string, all bool, files ...string) error {
 	return err
 }
 
+// CommitChangesOptions the options when a commit created
 type CommitChangesOptions struct {
 	Committer *Signature
 	Author    *Signature
@@ -166,22 +168,27 @@ func CommitsCount(repoPath, revision string) (int64, error) {
 	return commitsCount(repoPath, revision, "")
 }
 
+// CommitsCount returns number of total commits of until current revision.
 func (c *Commit) CommitsCount() (int64, error) {
 	return CommitsCount(c.repo.Path, c.ID.String())
 }
 
+// CommitsByRange returns the specific page commits before current revision, every page's number default by CommitsRangeSize
 func (c *Commit) CommitsByRange(page int) (*list.List, error) {
 	return c.repo.commitsByRange(c.ID, page)
 }
 
+// CommitsBefore returns all the commits before current revision
 func (c *Commit) CommitsBefore() (*list.List, error) {
 	return c.repo.getCommitsBefore(c.ID)
 }
 
+// CommitsBeforeLimit returns num commits before current revision
 func (c *Commit) CommitsBeforeLimit(num int) (*list.List, error) {
 	return c.repo.getCommitsBeforeLimit(c.ID, num)
 }
 
+// CommitsBeforeUntil returns the commits between commitID to current revision
 func (c *Commit) CommitsBeforeUntil(commitID string) (*list.List, error) {
 	endCommit, err := c.repo.GetCommit(commitID)
 	if err != nil {
@@ -190,15 +197,18 @@ func (c *Commit) CommitsBeforeUntil(commitID string) (*list.List, error) {
 	return c.repo.CommitsBetween(c, endCommit)
 }
 
+// SearchCommits returns the commits match the keyword before current revision
 func (c *Commit) SearchCommits(keyword string) (*list.List, error) {
 	return c.repo.searchCommits(c.ID, keyword)
 }
 
+// GetFilesChangedSinceCommit get all changed file names between pastCommit to current revision
 func (c *Commit) GetFilesChangedSinceCommit(pastCommit string) ([]string, error) {
 	return c.repo.getFilesChanged(pastCommit, c.ID.String())
 }
 
-func (c *Commit) GetSubModules() (*objectCache, error) {
+// GetSubModules get all the sub modules of current revision git tree
+func (c *Commit) GetSubModules() (*ObjectCache, error) {
 	if c.submoduleCache != nil {
 		return c.submoduleCache, nil
 	}
@@ -236,6 +246,7 @@ func (c *Commit) GetSubModules() (*objectCache, error) {
 	return c.submoduleCache, nil
 }
 
+// GetSubModule get the sub module according entryname
 func (c *Commit) GetSubModule(entryname string) (*SubModule, error) {
 	modules, err := c.GetSubModules()
 	if err != nil {
diff --git a/commit_archive.go b/commit_archive.go
index 1066ba6..e13825a 100644
--- a/commit_archive.go
+++ b/commit_archive.go
@@ -10,13 +10,17 @@ import (
 	"strings"
 )
 
+// ArchiveType archive types
 type ArchiveType int
 
 const (
+	// ZIP zip archive type
 	ZIP ArchiveType = iota + 1
+	// TARGZ tar gz archive type
 	TARGZ
 )
 
+// CreateArchive create archive content to the target path
 func (c *Commit) CreateArchive(target string, archiveType ArchiveType) error {
 	var format string
 	switch archiveType {
diff --git a/error.go b/error.go
index 848bfba..4fd2a5b 100644
--- a/error.go
+++ b/error.go
@@ -9,10 +9,12 @@ import (
 	"time"
 )
 
+// ErrExecTimeout error when exec timed out
 type ErrExecTimeout struct {
 	Duration time.Duration
 }
 
+// IsErrExecTimeout if some error is ErrExecTimeout
 func IsErrExecTimeout(err error) bool {
 	_, ok := err.(ErrExecTimeout)
 	return ok
@@ -22,11 +24,13 @@ func (err ErrExecTimeout) Error() string {
 	return fmt.Sprintf("execution is timeout [duration: %v]", err.Duration)
 }
 
+// ErrNotExist commit not exist error
 type ErrNotExist struct {
 	ID      string
 	RelPath string
 }
 
+// IsErrNotExist if some error is ErrNotExist
 func IsErrNotExist(err error) bool {
 	_, ok := err.(ErrNotExist)
 	return ok
@@ -36,10 +40,12 @@ func (err ErrNotExist) Error() string {
 	return fmt.Sprintf("object does not exist [id: %s, rel_path: %s]", err.ID, err.RelPath)
 }
 
+// ErrUnsupportedVersion error when required git version not matched
 type ErrUnsupportedVersion struct {
 	Required string
 }
 
+// IsErrUnsupportedVersion if some error is ErrUnsupportedVersion
 func IsErrUnsupportedVersion(err error) bool {
 	_, ok := err.(ErrUnsupportedVersion)
 	return ok
diff --git a/git.go b/git.go
index 71a9a37..2cea1dc 100644
--- a/git.go
+++ b/git.go
@@ -10,16 +10,16 @@ import (
 	"time"
 )
 
-const _VERSION = "0.4.2"
-
+// Version return this package's current version
 func Version() string {
-	return _VERSION
+	return "0.4.2"
 }
 
 var (
 	// Debug enables verbose logging on everything.
 	// This should be false in case Gogs starts in SSH mode.
-	Debug  = false
+	Debug = false
+	// Prefix the log prefix
 	Prefix = "[git-module] "
 )
 
@@ -38,7 +38,7 @@ func log(format string, args ...interface{}) {
 
 var gitVersion string
 
-// Version returns current Git version from shell.
+// BinVersion returns current Git version from shell.
 func BinVersion() (string, error) {
 	if len(gitVersion) > 0 {
 		return gitVersion, nil
diff --git a/hook.go b/hook.go
index 086bf71..d8069b6 100644
--- a/hook.go
+++ b/hook.go
@@ -22,6 +22,7 @@ var hookNames = []string{
 }
 
 var (
+	// ErrNotValidHook error when a git hook is not valid
 	ErrNotValidHook = errors.New("not a valid Git hook")
 )
 
@@ -70,6 +71,7 @@ func GetHook(repoPath, name string) (*Hook, error) {
 	return h, nil
 }
 
+// Name return the name of the hook
 func (h *Hook) Name() string {
 	return h.name
 }
@@ -102,6 +104,7 @@ func ListHooks(repoPath string) (_ []*Hook, err error) {
 }
 
 const (
+	// HookPathUpdate hook update path
 	HookPathUpdate = "hooks/update"
 )
 
diff --git a/repo.go b/repo.go
index 3d6c138..e596b74 100644
--- a/repo.go
+++ b/repo.go
@@ -18,11 +18,11 @@ import (
 type Repository struct {
 	Path string
 
-	commitCache *objectCache
-	tagCache    *objectCache
+	commitCache *ObjectCache
+	tagCache    *ObjectCache
 }
 
-const _PRETTY_LOG_FORMAT = `--pretty=format:%H`
+const prettyLogFormat = `--pretty=format:%H`
 
 func (repo *Repository) parsePrettyFormatLogToList(logs []byte) (*list.List, error) {
 	l := list.New()
@@ -32,8 +32,8 @@ func (repo *Repository) parsePrettyFormatLogToList(logs []byte) (*list.List, err
 
 	parts := bytes.Split(logs, []byte{'\n'})
 
-	for _, commitId := range parts {
-		commit, err := repo.GetCommit(string(commitId))
+	for _, commitID := range parts {
+		commit, err := repo.GetCommit(string(commitID))
 		if err != nil {
 			return nil, err
 		}
@@ -80,6 +80,7 @@ func OpenRepository(repoPath string) (*Repository, error) {
 	}, nil
 }
 
+// CloneRepoOptions options when clone a repository
 type CloneRepoOptions struct {
 	Timeout time.Duration
 	Mirror  bool
@@ -118,6 +119,7 @@ func Clone(from, to string, opts CloneRepoOptions) (err error) {
 	return err
 }
 
+// PullRemoteOptions options when pull from remote
 type PullRemoteOptions struct {
 	Timeout time.Duration
 	All     bool
@@ -153,6 +155,7 @@ func Push(repoPath, remote, branch string) error {
 	return err
 }
 
+// CheckoutOptions options when heck out some branch
 type CheckoutOptions struct {
 	Timeout   time.Duration
 	Branch    string
diff --git a/repo_branch.go b/repo_branch.go
index f7252bb..f2e9f43 100644
--- a/repo_branch.go
+++ b/repo_branch.go
@@ -11,7 +11,8 @@ import (
 	"github.com/mcuadros/go-version"
 )
 
-const BRANCH_PREFIX = "refs/heads/"
+// BranchPrefix base dir of the branch information file store on git
+const BranchPrefix = "refs/heads/"
 
 // IsReferenceExist returns true if given reference exists in the repository.
 func IsReferenceExist(repoPath, name string) bool {
@@ -21,9 +22,10 @@ func IsReferenceExist(repoPath, name string) bool {
 
 // IsBranchExist returns true if given branch exists in the repository.
 func IsBranchExist(repoPath, name string) bool {
-	return IsReferenceExist(repoPath, BRANCH_PREFIX+name)
+	return IsReferenceExist(repoPath, BranchPrefix+name)
 }
 
+// IsBranchExist returns true if given branch exists in current repository.
 func (repo *Repository) IsBranchExist(name string) bool {
 	return IsBranchExist(repo.Path, name)
 }
@@ -42,12 +44,12 @@ func (repo *Repository) GetHEADBranch() (*Branch, error) {
 	}
 	stdout = strings.TrimSpace(stdout)
 
-	if !strings.HasPrefix(stdout, BRANCH_PREFIX) {
+	if !strings.HasPrefix(stdout, BranchPrefix) {
 		return nil, fmt.Errorf("invalid HEAD branch: %v", stdout)
 	}
 
 	return &Branch{
-		Name: stdout[len(BRANCH_PREFIX):],
+		Name: stdout[len(BranchPrefix):],
 		Path: stdout,
 	}, nil
 }
@@ -58,7 +60,7 @@ func (repo *Repository) SetDefaultBranch(name string) error {
 		return ErrUnsupportedVersion{"1.7.10"}
 	}
 
-	_, err := NewCommand("symbolic-ref", "HEAD", BRANCH_PREFIX+name).RunInDir(repo.Path)
+	_, err := NewCommand("symbolic-ref", "HEAD", BranchPrefix+name).RunInDir(repo.Path)
 	return err
 }
 
@@ -76,12 +78,12 @@ func (repo *Repository) GetBranches() ([]string, error) {
 		if len(fields) != 2 {
 			continue // NOTE: I should believe git will not give me wrong string.
 		}
-		branches[i] = strings.TrimPrefix(fields[1], BRANCH_PREFIX)
+		branches[i] = strings.TrimPrefix(fields[1], BranchPrefix)
 	}
 	return branches, nil
 }
 
-// Option(s) for delete branch
+// DeleteBranchOptions Option(s) for delete branch
 type DeleteBranchOptions struct {
 	Force bool
 }
diff --git a/repo_commit.go b/repo_commit.go
index 1e7e51a..133d794 100644
--- a/repo_commit.go
+++ b/repo_commit.go
@@ -28,12 +28,12 @@ func (repo *Repository) getRefCommitID(name string) (string, error) {
 
 // GetBranchCommitID returns last commit ID string of given branch.
 func (repo *Repository) GetBranchCommitID(name string) (string, error) {
-	return repo.getRefCommitID(BRANCH_PREFIX + name)
+	return repo.getRefCommitID(BranchPrefix + name)
 }
 
 // GetTagCommitID returns last commit ID string of given tag.
 func (repo *Repository) GetTagCommitID(name string) (string, error) {
-	return repo.getRefCommitID(TAG_PREFIX + name)
+	return repo.getRefCommitID(TagPrefix + name)
 }
 
 // parseCommitData parses commit information from the (uncompressed) raw
@@ -41,7 +41,7 @@ func (repo *Repository) GetTagCommitID(name string) (string, error) {
 // \n\n separate headers from message
 func parseCommitData(data []byte) (*Commit, error) {
 	commit := new(Commit)
-	commit.parents = make([]sha1, 0, 1)
+	commit.parents = make([]SHA1, 0, 1)
 	// we now have the contents of the commit object. Let's investigate...
 	nextline := 0
 l:
@@ -90,7 +90,7 @@ l:
 	return commit, nil
 }
 
-func (repo *Repository) getCommit(id sha1) (*Commit, error) {
+func (repo *Repository) getCommit(id SHA1) (*Commit, error) {
 	c, ok := repo.commitCache.Get(id.String())
 	if ok {
 		log("Hit cache: %s", id)
@@ -142,6 +142,7 @@ func (repo *Repository) GetBranchCommit(name string) (*Commit, error) {
 	return repo.GetCommit(commitID)
 }
 
+// GetTagCommit get the commit of the specific tag via name
 func (repo *Repository) GetTagCommit(name string) (*Commit, error) {
 	commitID, err := repo.GetTagCommitID(name)
 	if err != nil {
@@ -150,13 +151,13 @@ func (repo *Repository) GetTagCommit(name string) (*Commit, error) {
 	return repo.GetCommit(commitID)
 }
 
-func (repo *Repository) getCommitByPathWithID(id sha1, relpath string) (*Commit, error) {
+func (repo *Repository) getCommitByPathWithID(id SHA1, relpath string) (*Commit, error) {
 	// File name starts with ':' must be escaped.
 	if relpath[0] == ':' {
 		relpath = `\` + relpath
 	}
 
-	stdout, err := NewCommand("log", "-1", _PRETTY_LOG_FORMAT, id.String(), "--", relpath).RunInDir(repo.Path)
+	stdout, err := NewCommand("log", "-1", prettyLogFormat, id.String(), "--", relpath).RunInDir(repo.Path)
 	if err != nil {
 		return nil, err
 	}
@@ -171,7 +172,7 @@ func (repo *Repository) getCommitByPathWithID(id sha1, relpath string) (*Commit,
 
 // GetCommitByPath returns the last commit of relative path.
 func (repo *Repository) GetCommitByPath(relpath string) (*Commit, error) {
-	stdout, err := NewCommand("log", "-1", _PRETTY_LOG_FORMAT, "--", relpath).RunInDirBytes(repo.Path)
+	stdout, err := NewCommand("log", "-1", prettyLogFormat, "--", relpath).RunInDirBytes(repo.Path)
 	if err != nil {
 		return nil, err
 	}
@@ -183,19 +184,20 @@ func (repo *Repository) GetCommitByPath(relpath string) (*Commit, error) {
 	return commits.Front().Value.(*Commit), nil
 }
 
+// CommitsRangeSize the default commits range size
 var CommitsRangeSize = 50
 
-func (repo *Repository) commitsByRange(id sha1, page int) (*list.List, error) {
+func (repo *Repository) commitsByRange(id SHA1, page int) (*list.List, error) {
 	stdout, err := NewCommand("log", id.String(), "--skip="+strconv.Itoa((page-1)*CommitsRangeSize),
-		"--max-count="+strconv.Itoa(CommitsRangeSize), _PRETTY_LOG_FORMAT).RunInDirBytes(repo.Path)
+		"--max-count="+strconv.Itoa(CommitsRangeSize), prettyLogFormat).RunInDirBytes(repo.Path)
 	if err != nil {
 		return nil, err
 	}
 	return repo.parsePrettyFormatLogToList(stdout)
 }
 
-func (repo *Repository) searchCommits(id sha1, keyword string) (*list.List, error) {
-	stdout, err := NewCommand("log", id.String(), "-100", "-i", "--grep="+keyword, _PRETTY_LOG_FORMAT).RunInDirBytes(repo.Path)
+func (repo *Repository) searchCommits(id SHA1, keyword string) (*list.List, error) {
+	stdout, err := NewCommand("log", id.String(), "-100", "-i", "--grep="+keyword, prettyLogFormat).RunInDirBytes(repo.Path)
 	if err != nil {
 		return nil, err
 	}
@@ -210,19 +212,22 @@ func (repo *Repository) getFilesChanged(id1 string, id2 string) ([]string, error
 	return strings.Split(string(stdout), "\n"), nil
 }
 
+// FileCommitsCount return the number of files at a revison
 func (repo *Repository) FileCommitsCount(revision, file string) (int64, error) {
 	return commitsCount(repo.Path, revision, file)
 }
 
+// CommitsByFileAndRange return the commits accroding revison file and the page
 func (repo *Repository) CommitsByFileAndRange(revision, file string, page int) (*list.List, error) {
 	stdout, err := NewCommand("log", revision, "--skip="+strconv.Itoa((page-1)*50),
-		"--max-count="+strconv.Itoa(CommitsRangeSize), _PRETTY_LOG_FORMAT, "--", file).RunInDirBytes(repo.Path)
+		"--max-count="+strconv.Itoa(CommitsRangeSize), prettyLogFormat, "--", file).RunInDirBytes(repo.Path)
 	if err != nil {
 		return nil, err
 	}
 	return repo.parsePrettyFormatLogToList(stdout)
 }
 
+// FilesCountBetween return the number of files changed between two commits
 func (repo *Repository) FilesCountBetween(startCommitID, endCommitID string) (int, error) {
 	stdout, err := NewCommand("diff", "--name-only", startCommitID+"..."+endCommitID).RunInDir(repo.Path)
 	if err != nil {
@@ -266,6 +271,7 @@ func (repo *Repository) CommitsBetween(last *Commit, before *Commit) (*list.List
 	return l, nil
 }
 
+// CommitsBetweenIDs return commits between twoe commits
 func (repo *Repository) CommitsBetweenIDs(last, before string) (*list.List, error) {
 	lastCommit, err := repo.GetCommit(last)
 	if err != nil {
@@ -278,12 +284,13 @@ func (repo *Repository) CommitsBetweenIDs(last, before string) (*list.List, erro
 	return repo.CommitsBetween(lastCommit, beforeCommit)
 }
 
+// CommitsCountBetween return numbers of commits between two commits
 func (repo *Repository) CommitsCountBetween(start, end string) (int64, error) {
 	return commitsCount(repo.Path, start+"..."+end, "")
 }
 
-// The limit is depth, not total number of returned commits.
-func (repo *Repository) commitsBefore(l *list.List, parent *list.Element, id sha1, current, limit int) error {
+// commitsBefore the limit is depth, not total number of returned commits.
+func (repo *Repository) commitsBefore(l *list.List, parent *list.Element, id SHA1, current, limit int) error {
 	// Reach the limit
 	if limit > 0 && current > limit {
 		return nil
@@ -342,12 +349,12 @@ func (repo *Repository) commitsBefore(l *list.List, parent *list.Element, id sha
 	return nil
 }
 
-func (repo *Repository) getCommitsBefore(id sha1) (*list.List, error) {
+func (repo *Repository) getCommitsBefore(id SHA1) (*list.List, error) {
 	l := list.New()
 	return l, repo.commitsBefore(l, nil, id, 1, 0)
 }
 
-func (repo *Repository) getCommitsBeforeLimit(id sha1, num int) (*list.List, error) {
+func (repo *Repository) getCommitsBeforeLimit(id SHA1, num int) (*list.List, error) {
 	l := list.New()
 	return l, repo.commitsBefore(l, nil, id, 1, num)
 }
diff --git a/repo_hook.go b/repo_hook.go
index 7b49647..49f4d09 100644
--- a/repo_hook.go
+++ b/repo_hook.go
@@ -4,10 +4,12 @@
 
 package git
 
+// GetHook get one hook accroding the name on a repository
 func (repo *Repository) GetHook(name string) (*Hook, error) {
 	return GetHook(repo.Path, name)
 }
 
+// Hooks get all the hooks on the repository
 func (repo *Repository) Hooks() ([]*Hook, error) {
 	return ListHooks(repo.Path)
 }
diff --git a/repo_object.go b/repo_object.go
index 416ee45..3be8400 100644
--- a/repo_object.go
+++ b/repo_object.go
@@ -4,11 +4,16 @@
 
 package git
 
+// ObjectType git object type
 type ObjectType string
 
 const (
-	OBJECT_COMMIT ObjectType = "commit"
-	OBJECT_TREE   ObjectType = "tree"
-	OBJECT_BLOB   ObjectType = "blob"
-	OBJECT_TAG    ObjectType = "tag"
+	// ObjectCommit commit object type
+	ObjectCommit ObjectType = "commit"
+	// ObjectTree tree object type
+	ObjectTree ObjectType = "tree"
+	// ObjectBlob blob object type
+	ObjectBlob ObjectType = "blob"
+	// ObjectTag tag object type
+	ObjectTag ObjectType = "tag"
 )
diff --git a/repo_pull.go b/repo_pull.go
index 1b0c1cf..1c45a4e 100644
--- a/repo_pull.go
+++ b/repo_pull.go
@@ -50,7 +50,7 @@ func (repo *Repository) GetPullRequestInfo(basePath, baseBranch, headBranch stri
 		return nil, fmt.Errorf("GetMergeBase: %v", err)
 	}
 
-	logs, err := NewCommand("log", prInfo.MergeBase+"..."+headBranch, _PRETTY_LOG_FORMAT).RunInDirBytes(repo.Path)
+	logs, err := NewCommand("log", prInfo.MergeBase+"..."+headBranch, prettyLogFormat).RunInDirBytes(repo.Path)
 	if err != nil {
 		return nil, err
 	}
diff --git a/repo_tag.go b/repo_tag.go
index 6a92f3c..dfaa41f 100644
--- a/repo_tag.go
+++ b/repo_tag.go
@@ -10,23 +10,26 @@ import (
 	"github.com/mcuadros/go-version"
 )
 
-const TAG_PREFIX = "refs/tags/"
+// TagPrefix tags prefix path on the repository
+const TagPrefix = "refs/tags/"
 
 // IsTagExist returns true if given tag exists in the repository.
 func IsTagExist(repoPath, name string) bool {
-	return IsReferenceExist(repoPath, TAG_PREFIX+name)
+	return IsReferenceExist(repoPath, TagPrefix+name)
 }
 
+// IsTagExist returns true if given tag exists in the repository.
 func (repo *Repository) IsTagExist(name string) bool {
 	return IsTagExist(repo.Path, name)
 }
 
+// CreateTag create one tag in the repository
 func (repo *Repository) CreateTag(name, revision string) error {
 	_, err := NewCommand("tag", name, revision).RunInDir(repo.Path)
 	return err
 }
 
-func (repo *Repository) getTag(id sha1) (*Tag, error) {
+func (repo *Repository) getTag(id SHA1) (*Tag, error) {
 	t, ok := repo.tagCache.Get(id.String())
 	if ok {
 		log("Hit cache: %s", id)
@@ -41,11 +44,11 @@ func (repo *Repository) getTag(id sha1) (*Tag, error) {
 	tp = strings.TrimSpace(tp)
 
 	// Tag is a commit.
-	if ObjectType(tp) == OBJECT_COMMIT {
+	if ObjectType(tp) == ObjectCommit {
 		tag := &Tag{
 			ID:     id,
 			Object: id,
-			Type:   string(OBJECT_COMMIT),
+			Type:   string(ObjectCommit),
 			repo:   repo,
 		}
 
diff --git a/repo_tree.go b/repo_tree.go
index baebb25..6e3843f 100644
--- a/repo_tree.go
+++ b/repo_tree.go
@@ -4,7 +4,7 @@
 
 package git
 
-func (repo *Repository) getTree(id sha1) (*Tree, error) {
+func (repo *Repository) getTree(id SHA1) (*Tree, error) {
 	treePath := filepathFromSHA1(repo.Path, id.String())
 	if isFile(treePath) {
 		_, err := NewCommand("ls-tree", id.String()).RunInDir(repo.Path)
@@ -16,7 +16,7 @@ func (repo *Repository) getTree(id sha1) (*Tree, error) {
 	return NewTree(repo, id), nil
 }
 
-// Find the tree object in the repository.
+// GetTree find the tree object in the repository.
 func (repo *Repository) GetTree(idStr string) (*Tree, error) {
 	id, err := NewIDFromString(idStr)
 	if err != nil {
diff --git a/sha1.go b/sha1.go
index 7744275..3f99535 100644
--- a/sha1.go
+++ b/sha1.go
@@ -10,13 +10,14 @@ import (
 	"strings"
 )
 
-const EMPTY_SHA = "0000000000000000000000000000000000000000"
+const emptySHA = "0000000000000000000000000000000000000000"
 
-type sha1 [20]byte
+// SHA1 a git commit name
+type SHA1 [20]byte
 
-// Equal returns true if s has the same sha1 as caller.
-// Support 40-length-string, []byte, sha1.
-func (id sha1) Equal(s2 interface{}) bool {
+// Equal returns true if s has the same SHA1 as caller.
+// Support 40-length-string, []byte, SHA1.
+func (id SHA1) Equal(s2 interface{}) bool {
 	switch v := s2.(type) {
 	case string:
 		if len(v) != 40 {
@@ -32,7 +33,7 @@ func (id sha1) Equal(s2 interface{}) bool {
 				return false
 			}
 		}
-	case sha1:
+	case SHA1:
 		for i, v := range v {
 			if id[i] != v {
 				return false
@@ -45,42 +46,42 @@ func (id sha1) Equal(s2 interface{}) bool {
 }
 
 // String returns string (hex) representation of the Oid.
-func (s sha1) String() string {
+func (id SHA1) String() string {
 	result := make([]byte, 0, 40)
 	hexvalues := []byte("0123456789abcdef")
 	for i := 0; i < 20; i++ {
-		result = append(result, hexvalues[s[i]>>4])
-		result = append(result, hexvalues[s[i]&0xf])
+		result = append(result, hexvalues[id[i]>>4])
+		result = append(result, hexvalues[id[i]&0xf])
 	}
 	return string(result)
 }
 
-// MustID always creates a new sha1 from a [20]byte array with no validation of input.
-func MustID(b []byte) sha1 {
-	var id sha1
+// MustID always creates a new SHA1 from a [20]byte array with no validation of input.
+func MustID(b []byte) SHA1 {
+	var id SHA1
 	for i := 0; i < 20; i++ {
 		id[i] = b[i]
 	}
 	return id
 }
 
-// NewID creates a new sha1 from a [20]byte array.
-func NewID(b []byte) (sha1, error) {
+// NewID creates a new SHA1 from a [20]byte array.
+func NewID(b []byte) (SHA1, error) {
 	if len(b) != 20 {
-		return sha1{}, fmt.Errorf("Length must be 20: %v", b)
+		return SHA1{}, fmt.Errorf("Length must be 20: %v", b)
 	}
 	return MustID(b), nil
 }
 
 // MustIDFromString always creates a new sha from a ID with no validation of input.
-func MustIDFromString(s string) sha1 {
+func MustIDFromString(s string) SHA1 {
 	b, _ := hex.DecodeString(s)
 	return MustID(b)
 }
 
-// NewIDFromString creates a new sha1 from a ID string of length 40.
-func NewIDFromString(s string) (sha1, error) {
-	var id sha1
+// NewIDFromString creates a new SHA1 from a ID string of length 40.
+func NewIDFromString(s string) (SHA1, error) {
+	var id SHA1
 	s = strings.TrimSpace(s)
 	if len(s) != 40 {
 		return id, fmt.Errorf("Length must be 40: %s", s)
diff --git a/submodule.go b/submodule.go
index 5777330..a0fe7b4 100644
--- a/submodule.go
+++ b/submodule.go
@@ -6,6 +6,7 @@ package git
 
 import "strings"
 
+// SubModule submodule is a reference on git repository
 type SubModule struct {
 	Name string
 	URL  string
@@ -19,6 +20,7 @@ type SubModuleFile struct {
 	refID  string
 }
 
+// NewSubModuleFile create a new submodule file
 func NewSubModuleFile(c *Commit, refURL, refID string) *SubModuleFile {
 	return &SubModuleFile{
 		Commit: c,
@@ -64,9 +66,8 @@ func (sf *SubModuleFile) RefURL(urlPrefix string, parentPath string) string {
 		// fix problem with reverse proxy works only with local server
 		if strings.Contains(urlPrefix, url[i+1:j]) {
 			return urlPrefix + url[j+1:]
-		} else {
-			return "http://" + url[i+1:j] + "/" + url[j+1:]
 		}
+		return "http://" + url[i+1:j] + "/" + url[j+1:]
 	}
 
 	return url
diff --git a/tag.go b/tag.go
index f4bf779..f2a3d31 100644
--- a/tag.go
+++ b/tag.go
@@ -9,14 +9,15 @@ import "bytes"
 // Tag represents a Git tag.
 type Tag struct {
 	Name    string
-	ID      sha1
+	ID      SHA1
 	repo    *Repository
-	Object  sha1 // The id of this commit object
+	Object  SHA1 // The id of this commit object
 	Type    string
 	Tagger  *Signature
 	Message string
 }
 
+// Commit return the commit of the tag reference
 func (tag *Tag) Commit() (*Commit, error) {
 	return tag.repo.getCommit(tag.Object)
 }
diff --git a/tree.go b/tree.go
index 8704282..05e7afd 100644
--- a/tree.go
+++ b/tree.go
@@ -12,7 +12,7 @@ import (
 
 // Tree represents a flat directory listing.
 type Tree struct {
-	ID   sha1
+	ID   SHA1
 	repo *Repository
 
 	// parent tree
@@ -22,7 +22,8 @@ type Tree struct {
 	entriesParsed bool
 }
 
-func NewTree(repo *Repository, id sha1) *Tree {
+// NewTree create a new tree according the repository and commit id
+func NewTree(repo *Repository, id SHA1) *Tree {
 	return &Tree{
 		ID:   id,
 		repo: repo,
@@ -63,22 +64,22 @@ func parseTreeData(tree *Tree, data []byte) ([]*TreeEntry, error) {
 		step := 6
 		switch string(data[pos : pos+step]) {
 		case "100644":
-			entry.mode = ENTRY_MODE_BLOB
-			entry.Type = OBJECT_BLOB
+			entry.mode = EntryModeBlob
+			entry.Type = ObjectBlob
 		case "100755":
-			entry.mode = ENTRY_MODE_EXEC
-			entry.Type = OBJECT_BLOB
+			entry.mode = EntryModeExec
+			entry.Type = ObjectBlob
 		case "120000":
-			entry.mode = ENTRY_MODE_SYMLINK
-			entry.Type = OBJECT_BLOB
+			entry.mode = EntryModeSymlink
+			entry.Type = ObjectBlob
 		case "160000":
-			entry.mode = ENTRY_MODE_COMMIT
-			entry.Type = OBJECT_COMMIT
+			entry.mode = EntryModeCommit
+			entry.Type = ObjectCommit
 
 			step = 8
 		case "040000":
-			entry.mode = ENTRY_MODE_TREE
-			entry.Type = OBJECT_TREE
+			entry.mode = EntryModeTree
+			entry.Type = ObjectTree
 		default:
 			return nil, fmt.Errorf("unknown type: %v", string(data[pos:pos+step]))
 		}
@@ -90,7 +91,7 @@ func parseTreeData(tree *Tree, data []byte) ([]*TreeEntry, error) {
 			return nil, err
 		}
 		entry.ID = id
-		pos += step + 1 // Skip half of sha1.
+		pos += step + 1 // Skip half of SHA1.
 
 		step = bytes.IndexByte(data[pos:], '\n')
 
@@ -107,6 +108,7 @@ func parseTreeData(tree *Tree, data []byte) ([]*TreeEntry, error) {
 	return entries, nil
 }
 
+// SubTree get a sub tree by the sub dir path
 func (t *Tree) SubTree(rpath string) (*Tree, error) {
 	if len(rpath) == 0 {
 		return t, nil
diff --git a/tree_blob.go b/tree_blob.go
index e2e7015..b3d205d 100644
--- a/tree_blob.go
+++ b/tree_blob.go
@@ -9,12 +9,13 @@ import (
 	"strings"
 )
 
+// GetTreeEntryByPath get the tree entries accroding the sub dir
 func (t *Tree) GetTreeEntryByPath(relpath string) (*TreeEntry, error) {
 	if len(relpath) == 0 {
 		return &TreeEntry{
 			ID:   t.ID,
-			Type: OBJECT_TREE,
-			mode: ENTRY_MODE_TREE,
+			Type: ObjectTree,
+			mode: EntryModeTree,
 		}, nil
 	}
 
@@ -43,6 +44,7 @@ func (t *Tree) GetTreeEntryByPath(relpath string) (*TreeEntry, error) {
 	return nil, ErrNotExist{"", relpath}
 }
 
+// GetBlobByPath get the blob object accroding the path
 func (t *Tree) GetBlobByPath(relpath string) (*Blob, error) {
 	entry, err := t.GetTreeEntryByPath(relpath)
 	if err != nil {
diff --git a/tree_entry.go b/tree_entry.go
index caad405..d3eefee 100644
--- a/tree_entry.go
+++ b/tree_entry.go
@@ -14,20 +14,27 @@ import (
 	"strings"
 )
 
+// EntryMode the type of the object in the git tree
 type EntryMode int
 
 // There are only a few file modes in Git. They look like unix file modes, but they can only be
 // one of these.
 const (
-	ENTRY_MODE_BLOB    EntryMode = 0100644
-	ENTRY_MODE_EXEC    EntryMode = 0100755
-	ENTRY_MODE_SYMLINK EntryMode = 0120000
-	ENTRY_MODE_COMMIT  EntryMode = 0160000
-	ENTRY_MODE_TREE    EntryMode = 0040000
+	// EntryModeBlob
+	EntryModeBlob EntryMode = 0100644
+	// EntryModeExec
+	EntryModeExec EntryMode = 0100755
+	// EntryModeSymlink
+	EntryModeSymlink EntryMode = 0120000
+	// EntryModeCommit
+	EntryModeCommit EntryMode = 0160000
+	// EntryModeTree
+	EntryModeTree EntryMode = 0040000
 )
 
+// TreeEntry the leaf in the git tree
 type TreeEntry struct {
-	ID   sha1
+	ID   SHA1
 	Type ObjectType
 
 	mode EntryMode
@@ -41,10 +48,12 @@ type TreeEntry struct {
 	sized bool
 }
 
+// Name returns the name of the entry
 func (te *TreeEntry) Name() string {
 	return te.name
 }
 
+// Size returns the size of the entry
 func (te *TreeEntry) Size() int64 {
 	if te.IsDir() {
 		return 0
@@ -62,14 +71,17 @@ func (te *TreeEntry) Size() int64 {
 	return te.size
 }
 
+// IsSubModule if the entry is a sub module
 func (te *TreeEntry) IsSubModule() bool {
-	return te.mode == ENTRY_MODE_COMMIT
+	return te.mode == EntryModeCommit
 }
 
+// IsDir if the entry is a sub dir
 func (te *TreeEntry) IsDir() bool {
-	return te.mode == ENTRY_MODE_TREE
+	return te.mode == EntryModeTree
 }
 
+// Blob retrun the blob object the entry
 func (te *TreeEntry) Blob() *Blob {
 	return &Blob{
 		repo:      te.ptree.repo,
@@ -77,6 +89,7 @@ func (te *TreeEntry) Blob() *Blob {
 	}
 }
 
+// Entries a list of entry
 type Entries []*TreeEntry
 
 var sorter = []func(t1, t2 *TreeEntry) bool{
@@ -105,6 +118,7 @@ func (tes Entries) Less(i, j int) bool {
 	return sorter[k](t1, t2)
 }
 
+// Sort sort the list of entry
 func (tes Entries) Sort() {
 	sort.Sort(tes)
 }
@@ -167,7 +181,7 @@ func (tes Entries) GetCommitsInfoWithCustomConcurrency(commit *Commit, treePath
 		// However when taskChan is full, code will block and wait any running goroutines to finish.
 		taskChan <- true
 
-		if tes[i].Type != OBJECT_COMMIT {
+		if tes[i].Type != ObjectCommit {
 			go func(i int) {
 				cinfo := commitInfo{entryName: tes[i].Name()}
 				c, err := commit.GetCommitByPath(filepath.Join(treePath, tes[i].Name()))
diff --git a/utils.go b/utils.go
index da8c581..8f01032 100644
--- a/utils.go
+++ b/utils.go
@@ -12,26 +12,28 @@ import (
 	"sync"
 )
 
-// objectCache provides thread-safe cache opeations.
-type objectCache struct {
+// ObjectCache provides thread-safe cache opeations.
+type ObjectCache struct {
 	lock  sync.RWMutex
 	cache map[string]interface{}
 }
 
-func newObjectCache() *objectCache {
-	return &objectCache{
+func newObjectCache() *ObjectCache {
+	return &ObjectCache{
 		cache: make(map[string]interface{}, 10),
 	}
 }
 
-func (oc *objectCache) Set(id string, obj interface{}) {
+// Set add obj to cache
+func (oc *ObjectCache) Set(id string, obj interface{}) {
 	oc.lock.Lock()
 	defer oc.lock.Unlock()
 
 	oc.cache[id] = obj
 }
 
-func (oc *objectCache) Get(id string) (interface{}, bool) {
+// Get get cached obj by id
+func (oc *ObjectCache) Get(id string) (interface{}, bool) {
 	oc.lock.RLock()
 	defer oc.lock.RUnlock()
 
@@ -80,13 +82,14 @@ func filepathFromSHA1(rootdir, sha1 string) string {
 	return filepath.Join(rootdir, "objects", sha1[:2], sha1[2:])
 }
 
+// RefEndName return the end name of a ref name
 func RefEndName(refStr string) string {
-	if strings.HasPrefix(refStr, BRANCH_PREFIX) {
-		return refStr[len(BRANCH_PREFIX):]
+	if strings.HasPrefix(refStr, BranchPrefix) {
+		return refStr[len(BranchPrefix):]
 	}
 
-	if strings.HasPrefix(refStr, TAG_PREFIX) {
-		return refStr[len(TAG_PREFIX):]
+	if strings.HasPrefix(refStr, TagPrefix) {
+		return refStr[len(TagPrefix):]
 	}
 
 	return refStr