func (d *VersionHandler) pkgPath(pkg string) string {
	root, sub := util.NormalizeName(pkg)

	// For the parent applications source skip the cache.
	if root == d.Config.Name {
		pth := gpath.Basepath()
		return filepath.Join(pth, filepath.FromSlash(sub))
	}

	dep := d.Config.Imports.Get(root)
	if dep == nil {
		dep = d.Config.DevImports.Get(root)
	}

	if dep == nil {
		dep, _ = d.Use.Get(root)

		if dep == nil {
			dep = &cfg.Dependency{Name: root}
		}
	}

	key, err := cache.Key(dep.Remote())
	if err != nil {
		msg.Die("Error generating cache key for %s", dep.Name)
	}

	return filepath.Join(cache.Location(), "src", key, filepath.FromSlash(sub))
}

// ConcurrentUpdate takes a list of dependencies and updates in parallel.
func ConcurrentUpdate(deps []*cfg.Dependency, i *Installer, c *cfg.Config) error {
	done := make(chan struct{}, concurrentWorkers)
	in := make(chan *cfg.Dependency, concurrentWorkers)
	var wg sync.WaitGroup
	var lock sync.Mutex
	var returnErr error

	for ii := 0; ii < concurrentWorkers; ii++ {
		go func(ch <-chan *cfg.Dependency) {
			for {
				select {
				case dep := <-ch:
					loc := dep.Remote()
					key, err := cache.Key(loc)
					if err != nil {
						msg.Die(err.Error())
					}
					cache.Lock(key)
					if err := VcsUpdate(dep, i.Force, i.Updated); err != nil {
						msg.Err("Update failed for %s: %s\n", dep.Name, err)
						// Capture the error while making sure the concurrent
						// operations don't step on each other.
						lock.Lock()
						if returnErr == nil {
							returnErr = err
						} else {
							returnErr = cli.NewMultiError(returnErr, err)
						}
						lock.Unlock()
					}
					cache.Unlock(key)
					wg.Done()
				case <-done:
					return
				}
			}
		}(in)
	}

	for _, dep := range deps {
		if !c.HasIgnore(dep.Name) {
			wg.Add(1)
			in <- dep
		}
	}

	wg.Wait()

	// Close goroutines setting the version
	for ii := 0; ii < concurrentWorkers; ii++ {
		done <- struct{}{}
	}

	return returnErr
}

// VcsGet figures out how to fetch a dependency, and then gets it.
//
// VcsGet installs into the cache.
func VcsGet(dep *cfg.Dependency) error {

	key, err := cp.Key(dep.Remote())
	if err != nil {
		msg.Die("Cache key generation error: %s", err)
	}
	location := cp.Location()
	d := filepath.Join(location, "src", key)

	repo, err := dep.GetRepo(d)
	if err != nil {
		return err
	}
	// If the directory does not exist this is a first cache.
	if _, err = os.Stat(d); os.IsNotExist(err) {
		msg.Debug("Adding %s to the cache for the first time", dep.Name)
		err = repo.Get()
		if err != nil {
			return err
		}
		branch := findCurrentBranch(repo)
		if branch != "" {
			msg.Debug("Saving default branch for %s", repo.Remote())
			c := cp.RepoInfo{DefaultBranch: branch}
			err = cp.SaveRepoData(key, c)
			if err == cp.ErrCacheDisabled {
				msg.Debug("Unable to cache default branch because caching is disabled")
			} else if err != nil {
				msg.Debug("Error saving %s to cache. Error: %s", repo.Remote(), err)
			}
		}
	} else {
		msg.Debug("Updating %s in the cache", dep.Name)
		err = repo.Update()
		if err != nil {
			return err
		}
	}

	return nil
}

// LazyConcurrentUpdate updates only deps that are not already checkout out at the right version.
//
// This is only safe when updating from a lock file.
func LazyConcurrentUpdate(deps []*cfg.Dependency, i *Installer, c *cfg.Config) error {

	newDeps := []*cfg.Dependency{}
	for _, dep := range deps {

		key, err := cache.Key(dep.Remote())
		if err != nil {
			newDeps = append(newDeps, dep)
			continue
		}
		destPath := filepath.Join(cache.Location(), "src", key)

		// Get a VCS object for this directory
		repo, err := dep.GetRepo(destPath)
		if err != nil {
			newDeps = append(newDeps, dep)
			continue
		}

		ver, err := repo.Version()
		if err != nil {
			newDeps = append(newDeps, dep)
			continue
		}
		if dep.Reference != "" {
			ci, err := repo.CommitInfo(dep.Reference)
			if err == nil && ci.Commit == dep.Reference {
				msg.Info("--> Found desired version locally %s %s!", dep.Name, dep.Reference)
				continue
			}
		}

		msg.Debug("--> Queue %s for update (%s != %s).", dep.Name, ver, dep.Reference)
		newDeps = append(newDeps, dep)
	}
	if len(newDeps) > 0 {
		return ConcurrentUpdate(newDeps, i, c)
	}

	return nil
}

func (d *VersionHandler) pkgPath(pkg string) string {
	root, sub := util.NormalizeName(pkg)

	dep := d.Config.Imports.Get(root)
	if dep == nil {
		dep = d.Config.DevImports.Get(root)
	}

	if dep == nil {
		dep, _ = d.Use.Get(root)

		if dep == nil {
			dep = &cfg.Dependency{Name: root}
		}
	}

	key, err := cache.Key(dep.Remote())
	if err != nil {
		msg.Die("Error generating cache key for %s", dep.Name)
	}

	return filepath.Join(cache.Location(), "src", key, sub)
}

// PkgPath resolves the location on the filesystem where the package should be.
// This handles making sure to use the cache location.
func (m *MissingPackageHandler) PkgPath(pkg string) string {
	root, sub := util.NormalizeName(pkg)

	d := m.Config.Imports.Get(root)
	if d == nil {
		d = m.Config.DevImports.Get(root)
	}

	if d == nil {
		d, _ = m.Use.Get(root)

		if d == nil {
			d = &cfg.Dependency{Name: root}
		}
	}

	key, err := cache.Key(d.Remote())
	if err != nil {
		msg.Die("Error generating cache key for %s", d.Name)
	}

	return filepath.Join(cache.Location(), "src", key, sub)
}

func wizardFindVersions(d *cfg.Dependency) {
	l, err := cache.Location()
	if err != nil {
		msg.Debug("Problem detecting cache location: %s", err)
		return
	}
	var remote string
	if d.Repository != "" {
		remote = d.Repository
	} else {
		remote = "https://" + d.Name
	}

	key, err := cache.Key(remote)
	if err != nil {
		msg.Debug("Problem generating cache key for %s: %s", remote, err)
		return
	}

	local := filepath.Join(l, "src", key)
	repo, err := vcs.NewRepo(remote, local)
	if err != nil {
		msg.Debug("Problem getting repo instance: %s", err)
		return
	}

	var useLocal bool
	if _, err = os.Stat(local); err == nil {
		useLocal = true
	}

	// Git endpoints allow for querying without fetching the codebase locally.
	// We try that first to avoid fetching right away. Is this premature
	// optimization?
	cc := true
	if !useLocal && repo.Vcs() == vcs.Git {
		out, err2 := exec.Command("git", "ls-remote", remote).CombinedOutput()
		if err2 == nil {
			cache.MemTouch(remote)
			cc = false
			lines := strings.Split(string(out), "\n")
			for _, i := range lines {
				ti := strings.TrimSpace(i)
				if found := createGitParseVersion.FindString(ti); found != "" {
					tg := strings.TrimPrefix(strings.TrimSuffix(found, "^{}"), "tags/")
					cache.MemPut(remote, tg)
					if d.Reference != "" && strings.HasPrefix(ti, d.Reference) {
						cache.MemSetCurrent(remote, tg)
					}
				}
			}
		}
	}

	if cc {
		cache.Lock(key)
		cache.MemTouch(remote)
		if _, err = os.Stat(local); os.IsNotExist(err) {
			repo.Get()
			branch := findCurrentBranch(repo)
			c := cache.RepoInfo{DefaultBranch: branch}
			err = cache.SaveRepoData(key, c)
			if err != nil {
				msg.Debug("Error saving cache repo details: %s", err)
			}
		} else {
			repo.Update()
		}
		tgs, err := repo.Tags()
		if err != nil {
			msg.Debug("Problem getting tags: %s", err)
		} else {
			for _, v := range tgs {
				cache.MemPut(remote, v)
			}
		}
		if d.Reference != "" && repo.IsReference(d.Reference) {
			tgs, err = repo.TagsFromCommit(d.Reference)
			if err != nil {
				msg.Debug("Problem getting tags for commit: %s", err)
			} else {
				if len(tgs) > 0 {
					for _, v := range tgs {
						if !(repo.Vcs() == vcs.Hg && v == "tip") {
							cache.MemSetCurrent(remote, v)
						}
					}
				}
			}
		}
		cache.Unlock(key)
	}
}

// ConcurrentUpdate takes a list of dependencies and updates in parallel.
func ConcurrentUpdate(deps []*cfg.Dependency, cwd string, i *Installer, c *cfg.Config) error {
	done := make(chan struct{}, concurrentWorkers)
	in := make(chan *cfg.Dependency, concurrentWorkers)
	var wg sync.WaitGroup
	var lock sync.Mutex
	var returnErr error

	msg.Info("Downloading dependencies. Please wait...")

	for ii := 0; ii < concurrentWorkers; ii++ {
		go func(ch <-chan *cfg.Dependency) {
			for {
				select {
				case dep := <-ch:
					var loc string
					if dep.Repository != "" {
						loc = dep.Repository
					} else {
						loc = "https://" + dep.Name
					}
					key, err := cache.Key(loc)
					if err != nil {
						msg.Die(err.Error())
					}
					cache.Lock(key)
					dest := filepath.Join(i.VendorPath(), dep.Name)
					if err := VcsUpdate(dep, dest, i.Home, i.UseCache, i.UseCacheGopath, i.UseGopath, i.Force, i.UpdateVendored, i.Updated); err != nil {
						msg.Err("Update failed for %s: %s\n", dep.Name, err)
						// Capture the error while making sure the concurrent
						// operations don't step on each other.
						lock.Lock()
						if returnErr == nil {
							returnErr = err
						} else {
							returnErr = cli.NewMultiError(returnErr, err)
						}
						lock.Unlock()
					}
					cache.Unlock(key)
					wg.Done()
				case <-done:
					return
				}
			}
		}(in)
	}

	for _, dep := range deps {
		if !c.HasIgnore(dep.Name) {
			wg.Add(1)
			in <- dep
		}
	}

	wg.Wait()

	// Close goroutines setting the version
	for ii := 0; ii < concurrentWorkers; ii++ {
		done <- struct{}{}
	}

	return returnErr
}

// Export from the cache to the vendor directory
func (i *Installer) Export(conf *cfg.Config) error {
	tempDir, err := ioutil.TempDir(gpath.Tmp, "glide-vendor")
	if err != nil {
		return err
	}
	defer func() {
		err = os.RemoveAll(tempDir)
		if err != nil {
			msg.Err(err.Error())
		}
	}()

	vp := filepath.Join(tempDir, "vendor")
	err = os.MkdirAll(vp, 0755)

	msg.Info("Exporting resolved dependencies...")
	done := make(chan struct{}, concurrentWorkers)
	in := make(chan *cfg.Dependency, concurrentWorkers)
	var wg sync.WaitGroup
	var lock sync.Mutex
	var returnErr error

	for ii := 0; ii < concurrentWorkers; ii++ {
		go func(ch <-chan *cfg.Dependency) {
			for {
				select {
				case dep := <-ch:
					loc := dep.Remote()
					key, err := cache.Key(loc)
					if err != nil {
						msg.Die(err.Error())
					}
					cache.Lock(key)

					cdir := filepath.Join(cache.Location(), "src", key)
					repo, err := dep.GetRepo(cdir)
					if err != nil {
						msg.Die(err.Error())
					}
					msg.Info("--> Exporting %s", dep.Name)
					if err := repo.ExportDir(filepath.Join(vp, filepath.ToSlash(dep.Name))); err != nil {
						msg.Err("Export failed for %s: %s\n", dep.Name, err)
						// Capture the error while making sure the concurrent
						// operations don't step on each other.
						lock.Lock()
						if returnErr == nil {
							returnErr = err
						} else {
							returnErr = cli.NewMultiError(returnErr, err)
						}
						lock.Unlock()
					}
					cache.Unlock(key)
					wg.Done()
				case <-done:
					return
				}
			}
		}(in)
	}

	for _, dep := range conf.Imports {
		if !conf.HasIgnore(dep.Name) {
			err = os.MkdirAll(filepath.Join(vp, filepath.ToSlash(dep.Name)), 0755)
			if err != nil {
				lock.Lock()
				if returnErr == nil {
					returnErr = err
				} else {
					returnErr = cli.NewMultiError(returnErr, err)
				}
				lock.Unlock()
			}
			wg.Add(1)
			in <- dep
		}
	}

	if i.ResolveTest {
		for _, dep := range conf.DevImports {
			if !conf.HasIgnore(dep.Name) {
				err = os.MkdirAll(filepath.Join(vp, filepath.ToSlash(dep.Name)), 0755)
				if err != nil {
					lock.Lock()
					if returnErr == nil {
						returnErr = err
					} else {
						returnErr = cli.NewMultiError(returnErr, err)
					}
					lock.Unlock()
				}
				wg.Add(1)
				in <- dep
			}
		}
	}

	wg.Wait()

//.........这里部分代码省略.........

// defaultBranch tries to ascertain the default branch for the given repo.
// Some repos will have multiple branches in them (e.g. Git) while others
// (e.g. Svn) will not.
func defaultBranch(repo v.Repo, home string) string {

	// Svn and Bzr use different locations (paths or entire locations)
	// for branches so we won't have a default branch.
	if repo.Vcs() == v.Svn || repo.Vcs() == v.Bzr {
		return ""
	}

	// Check the cache for a value.
	key, kerr := cp.Key(repo.Remote())
	var d cp.RepoInfo
	if kerr == nil {
		d, err := cp.RepoData(key)
		if err == nil {
			if d.DefaultBranch != "" {
				return d.DefaultBranch
			}
		}
	}

	// If we don't have it in the store try some APIs
	r := repo.Remote()
	u, err := url.Parse(r)
	if err != nil {
		return ""
	}
	if u.Scheme == "" {
		// Where there is no scheme we try urls like [email protected]:foo/bar
		r = strings.Replace(r, ":", "/", -1)
		r = "ssh://" + r
		u, err = url.Parse(r)
		if err != nil {
			return ""
		}
		u.Scheme = ""
	}
	if u.Host == "github.com" {
		parts := strings.Split(u.Path, "/")
		if len(parts) != 2 {
			return ""
		}
		api := fmt.Sprintf("https://api.github.com/repos/%s/%s", parts[0], parts[1])
		resp, err := http.Get(api)
		if err != nil {
			return ""
		}
		defer resp.Body.Close()
		if resp.StatusCode >= 300 || resp.StatusCode < 200 {
			return ""
		}
		body, err := ioutil.ReadAll(resp.Body)
		var data interface{}
		err = json.Unmarshal(body, &data)
		if err != nil {
			return ""
		}
		gh := data.(map[string]interface{})
		db := gh["default_branch"].(string)
		if kerr == nil {
			d.DefaultBranch = db
			err := cp.SaveRepoData(key, d)
			if err == cp.ErrCacheDisabled {
				msg.Debug("Unable to cache default branch because caching is disabled")
			} else if err != nil {
				msg.Debug("Error saving %s to cache. Error: %s", repo.Remote(), err)
			}
		}
		return db
	}

	if u.Host == "bitbucket.org" {
		parts := strings.Split(u.Path, "/")
		if len(parts) != 2 {
			return ""
		}
		api := fmt.Sprintf("https://bitbucket.org/api/1.0/repositories/%s/%s/main-branch/", parts[0], parts[1])
		resp, err := http.Get(api)
		if err != nil {
			return ""
		}
		defer resp.Body.Close()
		if resp.StatusCode >= 300 || resp.StatusCode < 200 {
			return ""
		}
		body, err := ioutil.ReadAll(resp.Body)
		var data interface{}
		err = json.Unmarshal(body, &data)
		if err != nil {
			return ""
		}
		bb := data.(map[string]interface{})
		db := bb["name"].(string)
		if kerr == nil {
			d.DefaultBranch = db
			err := cp.SaveRepoData(key, d)
			if err == cp.ErrCacheDisabled {
				msg.Debug("Unable to cache default branch because caching is disabled")
//.........这里部分代码省略.........

// VcsGet figures out how to fetch a dependency, and then gets it.
//
// VcsGet installs into the dest.
func VcsGet(dep *cfg.Dependency, dest, home string, cache, cacheGopath, useGopath bool) error {
	// When not skipping the $GOPATH look in it for a copy of the package
	if useGopath {
		// Check if the $GOPATH has a viable version to use and if so copy to vendor
		gps := gpath.Gopaths()
		for _, p := range gps {
			d := filepath.Join(p, "src", dep.Name)
			if _, err := os.Stat(d); err == nil {
				empty, err := gpath.IsDirectoryEmpty(d)
				if empty || err != nil {
					continue
				}

				repo, err := dep.GetRepo(d)
				if err != nil {
					continue
				}

				// Dirty repos have uncommitted changes.
				if repo.IsDirty() {
					continue
				}

				// Having found a repo we copy it to vendor and update it.
				msg.Info("Copying package %s from the GOPATH.", dep.Name)
				msg.Debug("Found %s in GOPATH at %s. Copying to %s", dep.Name, d, dest)
				err = gpath.CopyDir(d, dest)
				if err != nil {
					return err
				}

				// Update the repo in the vendor directory
				msg.Debug("Updating %s, now in the vendor path at %s", dep.Name, dest)
				repo, err = dep.GetRepo(dest)
				if err != nil {
					return err
				}
				err = repo.Update()
				if err != nil {
					return err
				}

				// If there is no reference set on the dep we try to checkout
				// the default branch.
				if dep.Reference == "" {
					db := defaultBranch(repo, home)
					if db != "" {
						err = repo.UpdateVersion(db)
						if err != nil && msg.Default.IsDebugging {
							msg.Debug("Attempting to set the version on %s to %s failed. Error %s", dep.Name, db, err)
						}
					}
				}
				return nil
			}
		}
	}

	// When opting in to cache in the GOPATH attempt to do put a copy there.
	if cacheGopath {

		// Since we didn't find an existing copy in the GOPATHs try to clone there.
		gp := gpath.Gopath()
		if gp != "" {
			d := filepath.Join(gp, "src", dep.Name)
			if _, err := os.Stat(d); os.IsNotExist(err) {
				// Empty directory so we checkout out the code here.
				msg.Debug("Retrieving %s to %s before copying to vendor", dep.Name, d)
				repo, err := dep.GetRepo(d)
				if err != nil {
					return err
				}
				repo.Get()

				branch := findCurrentBranch(repo)
				if branch != "" {
					// we know the default branch so we can store it in the cache
					var loc string
					if dep.Repository != "" {
						loc = dep.Repository
					} else {
						loc = "https://" + dep.Name
					}
					key, err := cp.Key(loc)
					if err == nil {
						msg.Debug("Saving default branch for %s", repo.Remote())
						c := cp.RepoInfo{DefaultBranch: branch}
						err = cp.SaveRepoData(key, c)
						if msg.Default.IsDebugging && err == cp.ErrCacheDisabled {
							msg.Debug("Unable to cache default branch because caching is disabled")
						}
					}
				}

				msg.Debug("Copying %s from GOPATH at %s to %s", dep.Name, d, dest)
				err = gpath.CopyDir(d, dest)
				if err != nil {
//.........这里部分代码省略.........

// SetReference is a command to set the VCS reference (commit id, tag, etc) for
// a project.
func SetReference(conf *cfg.Config, resolveTest bool) error {

	if len(conf.Imports) == 0 && len(conf.DevImports) == 0 {
		msg.Info("No references set.\n")
		return nil
	}

	done := make(chan struct{}, concurrentWorkers)
	in := make(chan *cfg.Dependency, concurrentWorkers)
	var wg sync.WaitGroup
	var lock sync.Mutex
	var returnErr error

	for i := 0; i < concurrentWorkers; i++ {
		go func(ch <-chan *cfg.Dependency) {
			for {
				select {
				case dep := <-ch:

					var loc string
					if dep.Repository != "" {
						loc = dep.Repository
					} else {
						loc = "https://" + dep.Name
					}
					key, err := cache.Key(loc)
					if err != nil {
						msg.Die(err.Error())
					}
					cache.Lock(key)
					if err := VcsVersion(dep); err != nil {
						msg.Err("Failed to set version on %s to %s: %s\n", dep.Name, dep.Reference, err)

						// Capture the error while making sure the concurrent
						// operations don't step on each other.
						lock.Lock()
						if returnErr == nil {
							returnErr = err
						} else {
							returnErr = cli.NewMultiError(returnErr, err)
						}
						lock.Unlock()
					}
					cache.Unlock(key)
					wg.Done()
				case <-done:
					return
				}
			}
		}(in)
	}

	for _, dep := range conf.Imports {
		if !conf.HasIgnore(dep.Name) {
			wg.Add(1)
			in <- dep
		}
	}

	if resolveTest {
		for _, dep := range conf.DevImports {
			if !conf.HasIgnore(dep.Name) {
				wg.Add(1)
				in <- dep
			}
		}
	}

	wg.Wait()
	// Close goroutines setting the version
	for i := 0; i < concurrentWorkers; i++ {
		done <- struct{}{}
	}
	// close(done)
	// close(in)

	return returnErr
}

// Export from the cache to the vendor directory
func (i *Installer) Export(conf *cfg.Config) error {
	tempDir, err := ioutil.TempDir(gpath.Tmp, "glide-vendor")
	if err != nil {
		return err
	}
	defer func() {
		err = os.RemoveAll(tempDir)
		if err != nil {
			msg.Err(err.Error())
		}
	}()

	vp := filepath.Join(tempDir, "vendor")
	err = os.MkdirAll(vp, 0755)

	msg.Info("Exporting resolved dependencies...")
	done := make(chan struct{}, concurrentWorkers)
	in := make(chan *cfg.Dependency, concurrentWorkers)
	var wg sync.WaitGroup
	var lock sync.Mutex
	var returnErr error

	for ii := 0; ii < concurrentWorkers; ii++ {
		go func(ch <-chan *cfg.Dependency) {
			for {
				select {
				case dep := <-ch:
					loc := dep.Remote()
					key, err := cache.Key(loc)
					if err != nil {
						msg.Die(err.Error())
					}
					cache.Lock(key)

					cdir := filepath.Join(cache.Location(), "src", key)
					repo, err := dep.GetRepo(cdir)
					if err != nil {
						msg.Die(err.Error())
					}
					msg.Info("--> Exporting %s", dep.Name)
					if err := repo.ExportDir(filepath.Join(vp, filepath.ToSlash(dep.Name))); err != nil {
						msg.Err("Export failed for %s: %s\n", dep.Name, err)
						// Capture the error while making sure the concurrent
						// operations don't step on each other.
						lock.Lock()
						if returnErr == nil {
							returnErr = err
						} else {
							returnErr = cli.NewMultiError(returnErr, err)
						}
						lock.Unlock()
					}
					cache.Unlock(key)
					wg.Done()
				case <-done:
					return
				}
			}
		}(in)
	}

	for _, dep := range conf.Imports {
		if !conf.HasIgnore(dep.Name) {
			err = os.MkdirAll(filepath.Join(vp, filepath.ToSlash(dep.Name)), 0755)
			if err != nil {
				lock.Lock()
				if returnErr == nil {
					returnErr = err
				} else {
					returnErr = cli.NewMultiError(returnErr, err)
				}
				lock.Unlock()
			}
			wg.Add(1)
			in <- dep
		}
	}

	if i.ResolveTest {
		for _, dep := range conf.DevImports {
			if !conf.HasIgnore(dep.Name) {
				err = os.MkdirAll(filepath.Join(vp, filepath.ToSlash(dep.Name)), 0755)
				if err != nil {
					lock.Lock()
					if returnErr == nil {
						returnErr = err
					} else {
						returnErr = cli.NewMultiError(returnErr, err)
					}
					lock.Unlock()
				}
				wg.Add(1)
				in <- dep
			}
		}
	}

	wg.Wait()

//.........这里部分代码省略.........

// VcsUpdate updates to a particular checkout based on the VCS setting.
func VcsUpdate(dep *cfg.Dependency, force bool, updated *UpdateTracker) error {

	// If the dependency has already been pinned we can skip it. This is a
	// faster path so we don't need to resolve it again.
	if dep.Pin != "" {
		msg.Debug("Dependency %s has already been pinned. Fetching updates skipped.", dep.Name)
		return nil
	}

	if updated.Check(dep.Name) {
		msg.Debug("%s was already updated, skipping.", dep.Name)
		return nil
	}
	updated.Add(dep.Name)

	if filterArchOs(dep) {
		msg.Info("%s is not used for %s/%s.\n", dep.Name, runtime.GOOS, runtime.GOARCH)
		return nil
	}

	key, err := cp.Key(dep.Remote())
	if err != nil {
		msg.Die("Cache key generation error: %s", err)
	}
	location := cp.Location()
	dest := filepath.Join(location, "src", key)

	// If destination doesn't exist we need to perform an initial checkout.
	if _, err := os.Stat(dest); os.IsNotExist(err) {
		msg.Info("--> Fetching %s.", dep.Name)
		if err = VcsGet(dep); err != nil {
			msg.Warn("Unable to checkout %s\n", dep.Name)
			return err
		}
	} else {
		// At this point we have a directory for the package.
		msg.Info("--> Fetching updates for %s.", dep.Name)

		// When the directory is not empty and has no VCS directory it's
		// a vendored files situation.
		empty, err := gpath.IsDirectoryEmpty(dest)
		if err != nil {
			return err
		}
		_, err = v.DetectVcsFromFS(dest)
		if empty == true && err == v.ErrCannotDetectVCS {
			msg.Warn("Cached version of %s is an empty directory. Fetching a new copy of the dependency.", dep.Name)
			msg.Debug("Removing empty directory %s", dest)
			err := os.RemoveAll(dest)
			if err != nil {
				return err
			}
			if err = VcsGet(dep); err != nil {
				msg.Warn("Unable to checkout %s\n", dep.Name)
				return err
			}
		} else {
			repo, err := dep.GetRepo(dest)

			// Tried to checkout a repo to a path that does not work. Either the
			// type or endpoint has changed. Force is being passed in so the old
			// location can be removed and replaced with the new one.
			// Warning, any changes in the old location will be deleted.
			// TODO: Put dirty checking in on the existing local checkout.
			if (err == v.ErrWrongVCS || err == v.ErrWrongRemote) && force == true {
				newRemote := dep.Remote()

				msg.Warn("Replacing %s with contents from %s\n", dep.Name, newRemote)
				rerr := os.RemoveAll(dest)
				if rerr != nil {
					return rerr
				}
				if err = VcsGet(dep); err != nil {
					msg.Warn("Unable to checkout %s\n", dep.Name)
					return err
				}

				repo, err = dep.GetRepo(dest)
				if err != nil {
					return err
				}
			} else if err != nil {
				return err
			} else if repo.IsDirty() {
				return fmt.Errorf("%s contains uncommitted changes. Skipping update", dep.Name)
			}

			ver := dep.Reference
			if ver == "" {
				ver = defaultBranch(repo)
			}
			// Check if the current version is a tag or commit id. If it is
			// and that version is already checked out we can skip updating
			// which is faster than going out to the Internet to perform
			// an update.
			if ver != "" {
				version, err := repo.Version()
				if err != nil {
					return err
//.........这里部分代码省略.........

// VcsVersion set the VCS version for a checkout.
func VcsVersion(dep *cfg.Dependency) error {

	// If the dependency has already been pinned we can skip it. This is a
	// faster path so we don't need to resolve it again.
	if dep.Pin != "" {
		msg.Debug("Dependency %s has already been pinned. Setting version skipped.", dep.Name)
		return nil
	}

	key, err := cp.Key(dep.Remote())
	if err != nil {
		msg.Die("Cache key generation error: %s", err)
	}
	location := cp.Location()
	cwd := filepath.Join(location, "src", key)

	// If there is no reference configured there is nothing to set.
	if dep.Reference == "" {
		// Before exiting update the pinned version
		repo, err := dep.GetRepo(cwd)
		if err != nil {
			return err
		}
		dep.Pin, err = repo.Version()
		if err != nil {
			return err
		}
		return nil
	}

	// When the directory is not empty and has no VCS directory it's
	// a vendored files situation.
	empty, err := gpath.IsDirectoryEmpty(cwd)
	if err != nil {
		return err
	}
	_, err = v.DetectVcsFromFS(cwd)
	if empty == false && err == v.ErrCannotDetectVCS {
		return fmt.Errorf("Cache directory missing VCS information for %s", dep.Name)
	}

	repo, err := dep.GetRepo(cwd)
	if err != nil {
		return err
	}

	ver := dep.Reference
	// References in Git can begin with a ^ which is similar to semver.
	// If there is a ^ prefix we assume it's a semver constraint rather than
	// part of the git/VCS commit id.
	if repo.IsReference(ver) && !strings.HasPrefix(ver, "^") {
		msg.Info("--> Setting version for %s to %s.\n", dep.Name, ver)
	} else {

		// Create the constraint first to make sure it's valid before
		// working on the repo.
		constraint, err := semver.NewConstraint(ver)

		// Make sure the constriant is valid. At this point it's not a valid
		// reference so if it's not a valid constrint we can exit early.
		if err != nil {
			msg.Warn("The reference '%s' is not valid\n", ver)
			return err
		}

		// Get the tags and branches (in that order)
		refs, err := getAllVcsRefs(repo)
		if err != nil {
			return err
		}

		// Convert and filter the list to semver.Version instances
		semvers := getSemVers(refs)

		// Sort semver list
		sort.Sort(sort.Reverse(semver.Collection(semvers)))
		found := false
		for _, v := range semvers {
			if constraint.Check(v) {
				found = true
				// If the constrint passes get the original reference
				ver = v.Original()
				break
			}
		}
		if found {
			msg.Info("--> Detected semantic version. Setting version for %s to %s.", dep.Name, ver)
		} else {
			msg.Warn("--> Unable to find semantic version for constraint %s %s", dep.Name, ver)
		}
	}
	if err := repo.UpdateVersion(ver); err != nil {
		return err
	}
	dep.Pin, err = repo.Version()
	if err != nil {
		return err
	}

//.........这里部分代码省略.........