cmd/pkg: Extract 'extra-sources' and adjust hash calculation

If the build.yml specifies 'extra-sources', ie sources
outside the package directory, calculate the hash based on
the tree hash of all source directories and the package
directory.

Note, this requires the source directories to be under
git revision control.

Also clean up the src and dst of the path and stash the
result in the Pkg structure.

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

src/cmd/linuxkit/pkglib/pkglib.go

@@ -1,11 +1,13 @@
 package pkglib
 
 import (
+	"crypto/sha1"
 	"flag"
 	"fmt"
 	"gopkg.in/yaml.v2"
 	"io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
 	"strings"
 
@@ -177,6 +179,37 @@ func NewFromCLI(fs *flag.FlagSet, args ...string) (Pkg, error) {
 		}
 	})
 
+	var srcHashes string
+	sources := []pkgSource{{src: pkgPath, dst: "/"}}
+
+	for _, source := range pi.ExtraSources {
+		tmp := strings.Split(source, ":")
+		if len(tmp) != 2 {
+			return Pkg{}, fmt.Errorf("Bad source format in %s", source)
+		}
+		srcPath := filepath.Clean(tmp[0]) // Should work with windows paths
+		dstPath := path.Clean(tmp[1])     // 'path' here because this should be a Unix path
+
+		if !filepath.IsAbs(srcPath) {
+			srcPath = filepath.Join(pkgPath, srcPath)
+		}
+
+		g, err := newGit(srcPath)
+		if err != nil {
+			return Pkg{}, err
+		}
+		if g == nil {
+			return Pkg{}, fmt.Errorf("Source %s not in a git repository", srcPath)
+		}
+		h, err := g.treeHash(srcPath, hashCommit)
+		if err != nil {
+			return Pkg{}, err
+		}
+
+		srcHashes += h
+		sources = append(sources, pkgSource{src: srcPath, dst: dstPath})
+	}
+
 	git, err := newGit(pkgPath)
 	if err != nil {
 		return Pkg{}, err
@@ -195,6 +228,11 @@ func NewFromCLI(fs *flag.FlagSet, args ...string) (Pkg, error) {
 				return Pkg{}, err
 			}
 
+			if srcHashes != "" {
+				hash += srcHashes
+				hash = fmt.Sprintf("%x", sha1.Sum([]byte(hash)))
+			}
+
 			if dirty {
 				hash += "-dirty"
 			}
@@ -207,7 +245,7 @@ func NewFromCLI(fs *flag.FlagSet, args ...string) (Pkg, error) {
 		hash:          hash,
 		commitHash:    hashCommit,
 		arches:        pi.Arches,
-		sources:       pi.Sources,
+		sources:       sources,
 		gitRepo:       pi.GitRepo,
 		network:       pi.Network,
 		trust:         !pi.DisableContentTrust,