Vendor main dependencies.

vendor/github.com/docker/docker/builder/builder.go

@@ -0,0 +1,169 @@
+// Package builder defines interfaces for any Docker builder to implement.
+//
+// Historically, only server-side Dockerfile interpreters existed.
+// This package allows for other implementations of Docker builders.
+package builder
+
+import (
+	"io"
+	"os"
+	"time"
+
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/api/types/backend"
+	"github.com/docker/docker/api/types/container"
+	"github.com/docker/docker/image"
+	"github.com/docker/docker/reference"
+	"golang.org/x/net/context"
+)
+
+const (
+	// DefaultDockerfileName is the Default filename with Docker commands, read by docker build
+	DefaultDockerfileName string = "Dockerfile"
+)
+
+// Context represents a file system tree.
+type Context interface {
+	// Close allows to signal that the filesystem tree won't be used anymore.
+	// For Context implementations using a temporary directory, it is recommended to
+	// delete the temporary directory in Close().
+	Close() error
+	// Stat returns an entry corresponding to path if any.
+	// It is recommended to return an error if path was not found.
+	// If path is a symlink it also returns the path to the target file.
+	Stat(path string) (string, FileInfo, error)
+	// Open opens path from the context and returns a readable stream of it.
+	Open(path string) (io.ReadCloser, error)
+	// Walk walks the tree of the context with the function passed to it.
+	Walk(root string, walkFn WalkFunc) error
+}
+
+// WalkFunc is the type of the function called for each file or directory visited by Context.Walk().
+type WalkFunc func(path string, fi FileInfo, err error) error
+
+// ModifiableContext represents a modifiable Context.
+// TODO: remove this interface once we can get rid of Remove()
+type ModifiableContext interface {
+	Context
+	// Remove deletes the entry specified by `path`.
+	// It is usual for directory entries to delete all its subentries.
+	Remove(path string) error
+}
+
+// FileInfo extends os.FileInfo to allow retrieving an absolute path to the file.
+// TODO: remove this interface once pkg/archive exposes a walk function that Context can use.
+type FileInfo interface {
+	os.FileInfo
+	Path() string
+}
+
+// PathFileInfo is a convenience struct that implements the FileInfo interface.
+type PathFileInfo struct {
+	os.FileInfo
+	// FilePath holds the absolute path to the file.
+	FilePath string
+	// Name holds the basename for the file.
+	FileName string
+}
+
+// Path returns the absolute path to the file.
+func (fi PathFileInfo) Path() string {
+	return fi.FilePath
+}
+
+// Name returns the basename of the file.
+func (fi PathFileInfo) Name() string {
+	if fi.FileName != "" {
+		return fi.FileName
+	}
+	return fi.FileInfo.Name()
+}
+
+// Hashed defines an extra method intended for implementations of os.FileInfo.
+type Hashed interface {
+	// Hash returns the hash of a file.
+	Hash() string
+	SetHash(string)
+}
+
+// HashedFileInfo is a convenient struct that augments FileInfo with a field.
+type HashedFileInfo struct {
+	FileInfo
+	// FileHash represents the hash of a file.
+	FileHash string
+}
+
+// Hash returns the hash of a file.
+func (fi HashedFileInfo) Hash() string {
+	return fi.FileHash
+}
+
+// SetHash sets the hash of a file.
+func (fi *HashedFileInfo) SetHash(h string) {
+	fi.FileHash = h
+}
+
+// Backend abstracts calls to a Docker Daemon.
+type Backend interface {
+	// TODO: use digest reference instead of name
+
+	// GetImageOnBuild looks up a Docker image referenced by `name`.
+	GetImageOnBuild(name string) (Image, error)
+	// TagImage tags an image with newTag
+	TagImageWithReference(image.ID, reference.Named) error
+	// PullOnBuild tells Docker to pull image referenced by `name`.
+	PullOnBuild(ctx context.Context, name string, authConfigs map[string]types.AuthConfig, output io.Writer) (Image, error)
+	// ContainerAttachRaw attaches to container.
+	ContainerAttachRaw(cID string, stdin io.ReadCloser, stdout, stderr io.Writer, stream bool) error
+	// ContainerCreate creates a new Docker container and returns potential warnings
+	ContainerCreate(config types.ContainerCreateConfig) (container.ContainerCreateCreatedBody, error)
+	// ContainerRm removes a container specified by `id`.
+	ContainerRm(name string, config *types.ContainerRmConfig) error
+	// Commit creates a new Docker image from an existing Docker container.
+	Commit(string, *backend.ContainerCommitConfig) (string, error)
+	// ContainerKill stops the container execution abruptly.
+	ContainerKill(containerID string, sig uint64) error
+	// ContainerStart starts a new container
+	ContainerStart(containerID string, hostConfig *container.HostConfig, checkpoint string, checkpointDir string) error
+	// ContainerWait stops processing until the given container is stopped.
+	ContainerWait(containerID string, timeout time.Duration) (int, error)
+	// ContainerUpdateCmdOnBuild updates container.Path and container.Args
+	ContainerUpdateCmdOnBuild(containerID string, cmd []string) error
+	// ContainerCreateWorkdir creates the workdir (currently only used on Windows)
+	ContainerCreateWorkdir(containerID string) error
+
+	// ContainerCopy copies/extracts a source FileInfo to a destination path inside a container
+	// specified by a container object.
+	// TODO: make an Extract method instead of passing `decompress`
+	// TODO: do not pass a FileInfo, instead refactor the archive package to export a Walk function that can be used
+	// with Context.Walk
+	// ContainerCopy(name string, res string) (io.ReadCloser, error)
+	// TODO: use copyBackend api
+	CopyOnBuild(containerID string, destPath string, src FileInfo, decompress bool) error
+
+	// HasExperimental checks if the backend supports experimental features
+	HasExperimental() bool
+
+	// SquashImage squashes the fs layers from the provided image down to the specified `to` image
+	SquashImage(from string, to string) (string, error)
+}
+
+// Image represents a Docker image used by the builder.
+type Image interface {
+	ImageID() string
+	RunConfig() *container.Config
+}
+
+// ImageCacheBuilder represents a generator for stateful image cache.
+type ImageCacheBuilder interface {
+	// MakeImageCache creates a stateful image cache.
+	MakeImageCache(cacheFrom []string) ImageCache
+}
+
+// ImageCache abstracts an image cache.
+// (parent image, child runconfig) -> child image
+type ImageCache interface {
+	// GetCachedImageOnBuild returns a reference to a cached image whose parent equals `parent`
+	// and runconfig equals `cfg`. A cache miss is expected to return an empty ID and a nil error.
+	GetCache(parentID string, cfg *container.Config) (imageID string, err error)
+}

vendor/github.com/docker/docker/builder/context.go

@@ -0,0 +1,260 @@
+package builder
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	"github.com/docker/docker/pkg/archive"
+	"github.com/docker/docker/pkg/fileutils"
+	"github.com/docker/docker/pkg/gitutils"
+	"github.com/docker/docker/pkg/httputils"
+	"github.com/docker/docker/pkg/ioutils"
+	"github.com/docker/docker/pkg/progress"
+	"github.com/docker/docker/pkg/streamformatter"
+)
+
+// ValidateContextDirectory checks if all the contents of the directory
+// can be read and returns an error if some files can't be read
+// symlinks which point to non-existing files don't trigger an error
+func ValidateContextDirectory(srcPath string, excludes []string) error {
+	contextRoot, err := getContextRoot(srcPath)
+	if err != nil {
+		return err
+	}
+	return filepath.Walk(contextRoot, func(filePath string, f os.FileInfo, err error) error {
+		if err != nil {
+			if os.IsPermission(err) {
+				return fmt.Errorf("can't stat '%s'", filePath)
+			}
+			if os.IsNotExist(err) {
+				return nil
+			}
+			return err
+		}
+
+		// skip this directory/file if it's not in the path, it won't get added to the context
+		if relFilePath, err := filepath.Rel(contextRoot, filePath); err != nil {
+			return err
+		} else if skip, err := fileutils.Matches(relFilePath, excludes); err != nil {
+			return err
+		} else if skip {
+			if f.IsDir() {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+
+		// skip checking if symlinks point to non-existing files, such symlinks can be useful
+		// also skip named pipes, because they hanging on open
+		if f.Mode()&(os.ModeSymlink|os.ModeNamedPipe) != 0 {
+			return nil
+		}
+
+		if !f.IsDir() {
+			currentFile, err := os.Open(filePath)
+			if err != nil && os.IsPermission(err) {
+				return fmt.Errorf("no permission to read from '%s'", filePath)
+			}
+			currentFile.Close()
+		}
+		return nil
+	})
+}
+
+// GetContextFromReader will read the contents of the given reader as either a
+// Dockerfile or tar archive. Returns a tar archive used as a context and a
+// path to the Dockerfile inside the tar.
+func GetContextFromReader(r io.ReadCloser, dockerfileName string) (out io.ReadCloser, relDockerfile string, err error) {
+	buf := bufio.NewReader(r)
+
+	magic, err := buf.Peek(archive.HeaderSize)
+	if err != nil && err != io.EOF {
+		return nil, "", fmt.Errorf("failed to peek context header from STDIN: %v", err)
+	}
+
+	if archive.IsArchive(magic) {
+		return ioutils.NewReadCloserWrapper(buf, func() error { return r.Close() }), dockerfileName, nil
+	}
+
+	// Input should be read as a Dockerfile.
+	tmpDir, err := ioutil.TempDir("", "docker-build-context-")
+	if err != nil {
+		return nil, "", fmt.Errorf("unbale to create temporary context directory: %v", err)
+	}
+
+	f, err := os.Create(filepath.Join(tmpDir, DefaultDockerfileName))
+	if err != nil {
+		return nil, "", err
+	}
+	_, err = io.Copy(f, buf)
+	if err != nil {
+		f.Close()
+		return nil, "", err
+	}
+
+	if err := f.Close(); err != nil {
+		return nil, "", err
+	}
+	if err := r.Close(); err != nil {
+		return nil, "", err
+	}
+
+	tar, err := archive.Tar(tmpDir, archive.Uncompressed)
+	if err != nil {
+		return nil, "", err
+	}
+
+	return ioutils.NewReadCloserWrapper(tar, func() error {
+		err := tar.Close()
+		os.RemoveAll(tmpDir)
+		return err
+	}), DefaultDockerfileName, nil
+
+}
+
+// GetContextFromGitURL uses a Git URL as context for a `docker build`. The
+// git repo is cloned into a temporary directory used as the context directory.
+// Returns the absolute path to the temporary context directory, the relative
+// path of the dockerfile in that context directory, and a non-nil error on
+// success.
+func GetContextFromGitURL(gitURL, dockerfileName string) (absContextDir, relDockerfile string, err error) {
+	if _, err := exec.LookPath("git"); err != nil {
+		return "", "", fmt.Errorf("unable to find 'git': %v", err)
+	}
+	if absContextDir, err = gitutils.Clone(gitURL); err != nil {
+		return "", "", fmt.Errorf("unable to 'git clone' to temporary context directory: %v", err)
+	}
+
+	return getDockerfileRelPath(absContextDir, dockerfileName)
+}
+
+// GetContextFromURL uses a remote URL as context for a `docker build`. The
+// remote resource is downloaded as either a Dockerfile or a tar archive.
+// Returns the tar archive used for the context and a path of the
+// dockerfile inside the tar.
+func GetContextFromURL(out io.Writer, remoteURL, dockerfileName string) (io.ReadCloser, string, error) {
+	response, err := httputils.Download(remoteURL)
+	if err != nil {
+		return nil, "", fmt.Errorf("unable to download remote context %s: %v", remoteURL, err)
+	}
+	progressOutput := streamformatter.NewStreamFormatter().NewProgressOutput(out, true)
+
+	// Pass the response body through a progress reader.
+	progReader := progress.NewProgressReader(response.Body, progressOutput, response.ContentLength, "", fmt.Sprintf("Downloading build context from remote url: %s", remoteURL))
+
+	return GetContextFromReader(ioutils.NewReadCloserWrapper(progReader, func() error { return response.Body.Close() }), dockerfileName)
+}
+
+// GetContextFromLocalDir uses the given local directory as context for a
+// `docker build`. Returns the absolute path to the local context directory,
+// the relative path of the dockerfile in that context directory, and a non-nil
+// error on success.
+func GetContextFromLocalDir(localDir, dockerfileName string) (absContextDir, relDockerfile string, err error) {
+	// When using a local context directory, when the Dockerfile is specified
+	// with the `-f/--file` option then it is considered relative to the
+	// current directory and not the context directory.
+	if dockerfileName != "" {
+		if dockerfileName, err = filepath.Abs(dockerfileName); err != nil {
+			return "", "", fmt.Errorf("unable to get absolute path to Dockerfile: %v", err)
+		}
+	}
+
+	return getDockerfileRelPath(localDir, dockerfileName)
+}
+
+// getDockerfileRelPath uses the given context directory for a `docker build`
+// and returns the absolute path to the context directory, the relative path of
+// the dockerfile in that context directory, and a non-nil error on success.
+func getDockerfileRelPath(givenContextDir, givenDockerfile string) (absContextDir, relDockerfile string, err error) {
+	if absContextDir, err = filepath.Abs(givenContextDir); err != nil {
+		return "", "", fmt.Errorf("unable to get absolute context directory of given context directory %q: %v", givenContextDir, err)
+	}
+
+	// The context dir might be a symbolic link, so follow it to the actual
+	// target directory.
+	//
+	// FIXME. We use isUNC (always false on non-Windows platforms) to workaround
+	// an issue in golang. On Windows, EvalSymLinks does not work on UNC file
+	// paths (those starting with \\). This hack means that when using links
+	// on UNC paths, they will not be followed.
+	if !isUNC(absContextDir) {
+		absContextDir, err = filepath.EvalSymlinks(absContextDir)
+		if err != nil {
+			return "", "", fmt.Errorf("unable to evaluate symlinks in context path: %v", err)
+		}
+	}
+
+	stat, err := os.Lstat(absContextDir)
+	if err != nil {
+		return "", "", fmt.Errorf("unable to stat context directory %q: %v", absContextDir, err)
+	}
+
+	if !stat.IsDir() {
+		return "", "", fmt.Errorf("context must be a directory: %s", absContextDir)
+	}
+
+	absDockerfile := givenDockerfile
+	if absDockerfile == "" {
+		// No -f/--file was specified so use the default relative to the
+		// context directory.
+		absDockerfile = filepath.Join(absContextDir, DefaultDockerfileName)
+
+		// Just to be nice ;-) look for 'dockerfile' too but only
+		// use it if we found it, otherwise ignore this check
+		if _, err = os.Lstat(absDockerfile); os.IsNotExist(err) {
+			altPath := filepath.Join(absContextDir, strings.ToLower(DefaultDockerfileName))
+			if _, err = os.Lstat(altPath); err == nil {
+				absDockerfile = altPath
+			}
+		}
+	}
+
+	// If not already an absolute path, the Dockerfile path should be joined to
+	// the base directory.
+	if !filepath.IsAbs(absDockerfile) {
+		absDockerfile = filepath.Join(absContextDir, absDockerfile)
+	}
+
+	// Evaluate symlinks in the path to the Dockerfile too.
+	//
+	// FIXME. We use isUNC (always false on non-Windows platforms) to workaround
+	// an issue in golang. On Windows, EvalSymLinks does not work on UNC file
+	// paths (those starting with \\). This hack means that when using links
+	// on UNC paths, they will not be followed.
+	if !isUNC(absDockerfile) {
+		absDockerfile, err = filepath.EvalSymlinks(absDockerfile)
+		if err != nil {
+			return "", "", fmt.Errorf("unable to evaluate symlinks in Dockerfile path: %v", err)
+		}
+	}
+
+	if _, err := os.Lstat(absDockerfile); err != nil {
+		if os.IsNotExist(err) {
+			return "", "", fmt.Errorf("Cannot locate Dockerfile: %q", absDockerfile)
+		}
+		return "", "", fmt.Errorf("unable to stat Dockerfile: %v", err)
+	}
+
+	if relDockerfile, err = filepath.Rel(absContextDir, absDockerfile); err != nil {
+		return "", "", fmt.Errorf("unable to get relative Dockerfile path: %v", err)
+	}
+
+	if strings.HasPrefix(relDockerfile, ".."+string(filepath.Separator)) {
+		return "", "", fmt.Errorf("The Dockerfile (%s) must be within the build context (%s)", givenDockerfile, givenContextDir)
+	}
+
+	return absContextDir, relDockerfile, nil
+}
+
+// isUNC returns true if the path is UNC (one starting \\). It always returns
+// false on Linux.
+func isUNC(path string) bool {
+	return runtime.GOOS == "windows" && strings.HasPrefix(path, `\\`)
+}

vendor/github.com/docker/docker/builder/context_unix.go

@@ -0,0 +1,11 @@
+// +build !windows
+
+package builder
+
+import (
+	"path/filepath"
+)
+
+func getContextRoot(srcPath string) (string, error) {
+	return filepath.Join(srcPath, "."), nil
+}

vendor/github.com/docker/docker/builder/context_windows.go

@@ -0,0 +1,17 @@
+// +build windows
+
+package builder
+
+import (
+	"path/filepath"
+
+	"github.com/docker/docker/pkg/longpath"
+)
+
+func getContextRoot(srcPath string) (string, error) {
+	cr, err := filepath.Abs(srcPath)
+	if err != nil {
+		return "", err
+	}
+	return longpath.AddPrefix(cr), nil
+}

vendor/github.com/docker/docker/builder/dockerignore.go

@@ -0,0 +1,48 @@
+package builder
+
+import (
+	"os"
+
+	"github.com/docker/docker/builder/dockerignore"
+	"github.com/docker/docker/pkg/fileutils"
+)
+
+// DockerIgnoreContext wraps a ModifiableContext to add a method
+// for handling the .dockerignore file at the root of the context.
+type DockerIgnoreContext struct {
+	ModifiableContext
+}
+
+// Process reads the .dockerignore file at the root of the embedded context.
+// If .dockerignore does not exist in the context, then nil is returned.
+//
+// It can take a list of files to be removed after .dockerignore is removed.
+// This is used for server-side implementations of builders that need to send
+// the .dockerignore file as well as the special files specified in filesToRemove,
+// but expect them to be excluded from the context after they were processed.
+//
+// For example, server-side Dockerfile builders are expected to pass in the name
+// of the Dockerfile to be removed after it was parsed.
+//
+// TODO: Don't require a ModifiableContext (use Context instead) and don't remove
+// files, instead handle a list of files to be excluded from the context.
+func (c DockerIgnoreContext) Process(filesToRemove []string) error {
+	f, err := c.Open(".dockerignore")
+	// Note that a missing .dockerignore file isn't treated as an error
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+	excludes, _ := dockerignore.ReadAll(f)
+	f.Close()
+	filesToRemove = append([]string{".dockerignore"}, filesToRemove...)
+	for _, fileToRemove := range filesToRemove {
+		rm, _ := fileutils.Matches(fileToRemove, excludes)
+		if rm {
+			c.Remove(fileToRemove)
+		}
+	}
+	return nil
+}

vendor/github.com/docker/docker/builder/dockerignore/dockerignore.go

@@ -0,0 +1,49 @@
+package dockerignore
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"path/filepath"
+	"strings"
+)
+
+// ReadAll reads a .dockerignore file and returns the list of file patterns
+// to ignore. Note this will trim whitespace from each line as well
+// as use GO's "clean" func to get the shortest/cleanest path for each.
+func ReadAll(reader io.Reader) ([]string, error) {
+	if reader == nil {
+		return nil, nil
+	}
+
+	scanner := bufio.NewScanner(reader)
+	var excludes []string
+	currentLine := 0
+
+	utf8bom := []byte{0xEF, 0xBB, 0xBF}
+	for scanner.Scan() {
+		scannedBytes := scanner.Bytes()
+		// We trim UTF8 BOM
+		if currentLine == 0 {
+			scannedBytes = bytes.TrimPrefix(scannedBytes, utf8bom)
+		}
+		pattern := string(scannedBytes)
+		currentLine++
+		// Lines starting with # (comments) are ignored before processing
+		if strings.HasPrefix(pattern, "#") {
+			continue
+		}
+		pattern = strings.TrimSpace(pattern)
+		if pattern == "" {
+			continue
+		}
+		pattern = filepath.Clean(pattern)
+		pattern = filepath.ToSlash(pattern)
+		excludes = append(excludes, pattern)
+	}
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("Error reading .dockerignore: %v", err)
+	}
+	return excludes, nil
+}

vendor/github.com/docker/docker/builder/git.go

@@ -0,0 +1,28 @@
+package builder
+
+import (
+	"os"
+
+	"github.com/docker/docker/pkg/archive"
+	"github.com/docker/docker/pkg/gitutils"
+)
+
+// MakeGitContext returns a Context from gitURL that is cloned in a temporary directory.
+func MakeGitContext(gitURL string) (ModifiableContext, error) {
+	root, err := gitutils.Clone(gitURL)
+	if err != nil {
+		return nil, err
+	}
+
+	c, err := archive.Tar(root, archive.Uncompressed)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		// TODO: print errors?
+		c.Close()
+		os.RemoveAll(root)
+	}()
+	return MakeTarSumContext(c)
+}

vendor/github.com/docker/docker/builder/remote.go

@@ -0,0 +1,157 @@
+package builder
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"regexp"
+
+	"github.com/docker/docker/pkg/archive"
+	"github.com/docker/docker/pkg/httputils"
+	"github.com/docker/docker/pkg/urlutil"
+)
+
+// When downloading remote contexts, limit the amount (in bytes)
+// to be read from the response body in order to detect its Content-Type
+const maxPreambleLength = 100
+
+const acceptableRemoteMIME = `(?:application/(?:(?:x\-)?tar|octet\-stream|((?:x\-)?(?:gzip|bzip2?|xz)))|(?:text/plain))`
+
+var mimeRe = regexp.MustCompile(acceptableRemoteMIME)
+
+// MakeRemoteContext downloads a context from remoteURL and returns it.
+//
+// If contentTypeHandlers is non-nil, then the Content-Type header is read along with a maximum of
+// maxPreambleLength bytes from the body to help detecting the MIME type.
+// Look at acceptableRemoteMIME for more details.
+//
+// If a match is found, then the body is sent to the contentType handler and a (potentially compressed) tar stream is expected
+// to be returned. If no match is found, it is assumed the body is a tar stream (compressed or not).
+// In either case, an (assumed) tar stream is passed to MakeTarSumContext whose result is returned.
+func MakeRemoteContext(remoteURL string, contentTypeHandlers map[string]func(io.ReadCloser) (io.ReadCloser, error)) (ModifiableContext, error) {
+	f, err := httputils.Download(remoteURL)
+	if err != nil {
+		return nil, fmt.Errorf("error downloading remote context %s: %v", remoteURL, err)
+	}
+	defer f.Body.Close()
+
+	var contextReader io.ReadCloser
+	if contentTypeHandlers != nil {
+		contentType := f.Header.Get("Content-Type")
+		clen := f.ContentLength
+
+		contentType, contextReader, err = inspectResponse(contentType, f.Body, clen)
+		if err != nil {
+			return nil, fmt.Errorf("error detecting content type for remote %s: %v", remoteURL, err)
+		}
+		defer contextReader.Close()
+
+		// This loop tries to find a content-type handler for the detected content-type.
+		// If it could not find one from the caller-supplied map, it tries the empty content-type `""`
+		// which is interpreted as a fallback handler (usually used for raw tar contexts).
+		for _, ct := range []string{contentType, ""} {
+			if fn, ok := contentTypeHandlers[ct]; ok {
+				defer contextReader.Close()
+				if contextReader, err = fn(contextReader); err != nil {
+					return nil, err
+				}
+				break
+			}
+		}
+	}
+
+	// Pass through - this is a pre-packaged context, presumably
+	// with a Dockerfile with the right name inside it.
+	return MakeTarSumContext(contextReader)
+}
+
+// DetectContextFromRemoteURL returns a context and in certain cases the name of the dockerfile to be used
+// irrespective of user input.
+// progressReader is only used if remoteURL is actually a URL (not empty, and not a Git endpoint).
+func DetectContextFromRemoteURL(r io.ReadCloser, remoteURL string, createProgressReader func(in io.ReadCloser) io.ReadCloser) (context ModifiableContext, dockerfileName string, err error) {
+	switch {
+	case remoteURL == "":
+		context, err = MakeTarSumContext(r)
+	case urlutil.IsGitURL(remoteURL):
+		context, err = MakeGitContext(remoteURL)
+	case urlutil.IsURL(remoteURL):
+		context, err = MakeRemoteContext(remoteURL, map[string]func(io.ReadCloser) (io.ReadCloser, error){
+			httputils.MimeTypes.TextPlain: func(rc io.ReadCloser) (io.ReadCloser, error) {
+				dockerfile, err := ioutil.ReadAll(rc)
+				if err != nil {
+					return nil, err
+				}
+
+				// dockerfileName is set to signal that the remote was interpreted as a single Dockerfile, in which case the caller
+				// should use dockerfileName as the new name for the Dockerfile, irrespective of any other user input.
+				dockerfileName = DefaultDockerfileName
+
+				// TODO: return a context without tarsum
+				r, err := archive.Generate(dockerfileName, string(dockerfile))
+				if err != nil {
+					return nil, err
+				}
+
+				return ioutil.NopCloser(r), nil
+			},
+			// fallback handler (tar context)
+			"": func(rc io.ReadCloser) (io.ReadCloser, error) {
+				return createProgressReader(rc), nil
+			},
+		})
+	default:
+		err = fmt.Errorf("remoteURL (%s) could not be recognized as URL", remoteURL)
+	}
+	return
+}
+
+// inspectResponse looks into the http response data at r to determine whether its
+// content-type is on the list of acceptable content types for remote build contexts.
+// This function returns:
+//    - a string representation of the detected content-type
+//    - an io.Reader for the response body
+//    - an error value which will be non-nil either when something goes wrong while
+//      reading bytes from r or when the detected content-type is not acceptable.
+func inspectResponse(ct string, r io.ReadCloser, clen int64) (string, io.ReadCloser, error) {
+	plen := clen
+	if plen <= 0 || plen > maxPreambleLength {
+		plen = maxPreambleLength
+	}
+
+	preamble := make([]byte, plen, plen)
+	rlen, err := r.Read(preamble)
+	if rlen == 0 {
+		return ct, r, errors.New("empty response")
+	}
+	if err != nil && err != io.EOF {
+		return ct, r, err
+	}
+
+	preambleR := bytes.NewReader(preamble)
+	bodyReader := ioutil.NopCloser(io.MultiReader(preambleR, r))
+	// Some web servers will use application/octet-stream as the default
+	// content type for files without an extension (e.g. 'Dockerfile')
+	// so if we receive this value we better check for text content
+	contentType := ct
+	if len(ct) == 0 || ct == httputils.MimeTypes.OctetStream {
+		contentType, _, err = httputils.DetectContentType(preamble)
+		if err != nil {
+			return contentType, bodyReader, err
+		}
+	}
+
+	contentType = selectAcceptableMIME(contentType)
+	var cterr error
+	if len(contentType) == 0 {
+		cterr = fmt.Errorf("unsupported Content-Type %q", ct)
+		contentType = ct
+	}
+
+	return contentType, bodyReader, cterr
+}
+
+func selectAcceptableMIME(ct string) string {
+	return mimeRe.FindString(ct)
+}

vendor/github.com/docker/docker/builder/tarsum.go

@@ -0,0 +1,158 @@
+package builder
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/docker/docker/pkg/archive"
+	"github.com/docker/docker/pkg/chrootarchive"
+	"github.com/docker/docker/pkg/ioutils"
+	"github.com/docker/docker/pkg/symlink"
+	"github.com/docker/docker/pkg/tarsum"
+)
+
+type tarSumContext struct {
+	root string
+	sums tarsum.FileInfoSums
+}
+
+func (c *tarSumContext) Close() error {
+	return os.RemoveAll(c.root)
+}
+
+func convertPathError(err error, cleanpath string) error {
+	if err, ok := err.(*os.PathError); ok {
+		err.Path = cleanpath
+		return err
+	}
+	return err
+}
+
+func (c *tarSumContext) Open(path string) (io.ReadCloser, error) {
+	cleanpath, fullpath, err := c.normalize(path)
+	if err != nil {
+		return nil, err
+	}
+	r, err := os.Open(fullpath)
+	if err != nil {
+		return nil, convertPathError(err, cleanpath)
+	}
+	return r, nil
+}
+
+func (c *tarSumContext) Stat(path string) (string, FileInfo, error) {
+	cleanpath, fullpath, err := c.normalize(path)
+	if err != nil {
+		return "", nil, err
+	}
+
+	st, err := os.Lstat(fullpath)
+	if err != nil {
+		return "", nil, convertPathError(err, cleanpath)
+	}
+
+	rel, err := filepath.Rel(c.root, fullpath)
+	if err != nil {
+		return "", nil, convertPathError(err, cleanpath)
+	}
+
+	// We set sum to path by default for the case where GetFile returns nil.
+	// The usual case is if relative path is empty.
+	sum := path
+	// Use the checksum of the followed path(not the possible symlink) because
+	// this is the file that is actually copied.
+	if tsInfo := c.sums.GetFile(filepath.ToSlash(rel)); tsInfo != nil {
+		sum = tsInfo.Sum()
+	}
+	fi := &HashedFileInfo{PathFileInfo{st, fullpath, filepath.Base(cleanpath)}, sum}
+	return rel, fi, nil
+}
+
+// MakeTarSumContext returns a build Context from a tar stream.
+//
+// It extracts the tar stream to a temporary folder that is deleted as soon as
+// the Context is closed.
+// As the extraction happens, a tarsum is calculated for every file, and the set of
+// all those sums then becomes the source of truth for all operations on this Context.
+//
+// Closing tarStream has to be done by the caller.
+func MakeTarSumContext(tarStream io.Reader) (ModifiableContext, error) {
+	root, err := ioutils.TempDir("", "docker-builder")
+	if err != nil {
+		return nil, err
+	}
+
+	tsc := &tarSumContext{root: root}
+
+	// Make sure we clean-up upon error.  In the happy case the caller
+	// is expected to manage the clean-up
+	defer func() {
+		if err != nil {
+			tsc.Close()
+		}
+	}()
+
+	decompressedStream, err := archive.DecompressStream(tarStream)
+	if err != nil {
+		return nil, err
+	}
+
+	sum, err := tarsum.NewTarSum(decompressedStream, true, tarsum.Version1)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := chrootarchive.Untar(sum, root, nil); err != nil {
+		return nil, err
+	}
+
+	tsc.sums = sum.GetSums()
+
+	return tsc, nil
+}
+
+func (c *tarSumContext) normalize(path string) (cleanpath, fullpath string, err error) {
+	cleanpath = filepath.Clean(string(os.PathSeparator) + path)[1:]
+	fullpath, err = symlink.FollowSymlinkInScope(filepath.Join(c.root, path), c.root)
+	if err != nil {
+		return "", "", fmt.Errorf("Forbidden path outside the build context: %s (%s)", path, fullpath)
+	}
+	_, err = os.Lstat(fullpath)
+	if err != nil {
+		return "", "", convertPathError(err, path)
+	}
+	return
+}
+
+func (c *tarSumContext) Walk(root string, walkFn WalkFunc) error {
+	root = filepath.Join(c.root, filepath.Join(string(filepath.Separator), root))
+	return filepath.Walk(root, func(fullpath string, info os.FileInfo, err error) error {
+		rel, err := filepath.Rel(c.root, fullpath)
+		if err != nil {
+			return err
+		}
+		if rel == "." {
+			return nil
+		}
+
+		sum := rel
+		if tsInfo := c.sums.GetFile(filepath.ToSlash(rel)); tsInfo != nil {
+			sum = tsInfo.Sum()
+		}
+		fi := &HashedFileInfo{PathFileInfo{FileInfo: info, FilePath: fullpath}, sum}
+		if err := walkFn(rel, fi, nil); err != nil {
+			return err
+		}
+		return nil
+	})
+}
+
+func (c *tarSumContext) Remove(path string) error {
+	_, fullpath, err := c.normalize(path)
+	if err != nil {
+		return err
+	}
+	return os.RemoveAll(fullpath)
+}