Merge pull request #2627 from ijc/linuxkit-pkg-no-git

Improve `linuxkit pkg` handling of git

src/cmd/linuxkit/pkglib/build.go

@@ -70,8 +70,8 @@ func (p Pkg) Build(bos ...BuildOpt) error {
 		return fmt.Errorf("Unknown arch %q", arch)
 	}
 
-	if bo.release == "" {
-		r, err := gitCommitTag("HEAD")
+	if p.git != nil && bo.release == "" {
+		r, err := p.git.commitTag("HEAD")
 		if err != nil {
 			return err
 		}
@@ -97,11 +97,11 @@ func (p Pkg) Build(bos ...BuildOpt) error {
 
 	var args []string
 
-	if p.gitRepo != "" {
+	if p.git != nil && p.gitRepo != "" {
 		args = append(args, "--label", "org.opencontainers.image.source="+p.gitRepo)
 	}
-	if !p.dirty {
-		commit, err := gitCommitHash("HEAD")
+	if p.git != nil && !p.dirty {
+		commit, err := p.git.commitHash("HEAD")
 		if err != nil {
 			return err
 		}

src/cmd/linuxkit/pkglib/git.go

@@ -4,6 +4,7 @@ package pkglib
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"os/exec"
 	"regexp"
@@ -19,9 +20,32 @@ func init() {
 	treeHashRe = regexp.MustCompile("^[0-7]{6} [^ ]+ ([0-9a-f]{40})\t.+\n$")
 }
 
-func gitCommandStdout(args ...string) (string, error) {
-	cmd := exec.Command("git", args...)
-	cmd.Stderr = os.Stderr
+type git struct {
+	dir string
+}
+
+// Returns git==nil and no error if the path is not within a git repository
+func newGit(dir string) (*git, error) {
+	g := &git{dir}
+
+	// Check if dir really is within a git directory
+	ok, err := g.isWorkTree(dir)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, nil
+	}
+	return g, nil
+}
+
+func (g git) mkCmd(args ...string) *exec.Cmd {
+	return exec.Command("git", append([]string{"-C", g.dir}, args...)...)
+}
+
+func (g git) commandStdout(stderr io.Writer, args ...string) (string, error) {
+	cmd := g.mkCmd(args...)
+	cmd.Stderr = stderr
 
 	if debugGitCommands {
 		fmt.Fprintf(os.Stderr, "+ %v\n", cmd.Args)
@@ -33,8 +57,8 @@ func gitCommandStdout(args ...string) (string, error) {
 	return string(out), nil
 }
 
-func gitCommand(args ...string) error {
-	cmd := exec.Command("git", args...)
+func (g git) command(args ...string) error {
+	cmd := g.mkCmd(args...)
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 	if debugGitCommands {
@@ -43,8 +67,27 @@ func gitCommand(args ...string) error {
 	return cmd.Run()
 }
 
-func gitTreeHash(pkg, commit string) (string, error) {
-	out, err := gitCommandStdout("ls-tree", "--full-tree", commit, "--", pkg)
+func (g git) isWorkTree(pkg string) (bool, error) {
+	tf, err := g.commandStdout(nil, "rev-parse", "--is-inside-work-tree")
+	if err != nil {
+		// If we executed git ok but it errored then that's because this isn't a git repo
+		if _, ok := err.(*exec.ExitError); ok {
+			return false, nil
+		}
+		return false, err
+	}
+
+	tf = strings.TrimSpace(tf)
+
+	if tf == "true" {
+		return true, nil
+	}
+
+	return false, fmt.Errorf("unexpected output from git rev-parse --is-inside-work-tree: %s", tf)
+}
+
+func (g git) treeHash(pkg, commit string) (string, error) {
+	out, err := g.commandStdout(os.Stderr, "ls-tree", "--full-tree", commit, "--", pkg)
 	if err != nil {
 		return "", err
 	}
@@ -57,8 +100,8 @@ func gitTreeHash(pkg, commit string) (string, error) {
 	return matches[1], nil
 }
 
-func gitCommitHash(commit string) (string, error) {
-	out, err := gitCommandStdout("rev-parse", commit)
+func (g git) commitHash(commit string) (string, error) {
+	out, err := g.commandStdout(os.Stderr, "rev-parse", commit)
 	if err != nil {
 		return "", err
 	}
@@ -66,8 +109,8 @@ func gitCommitHash(commit string) (string, error) {
 	return strings.TrimSpace(out), nil
 }
 
-func gitCommitTag(commit string) (string, error) {
-	out, err := gitCommandStdout("tag", "-l", "--points-at", commit)
+func (g git) commitTag(commit string) (string, error) {
+	out, err := g.commandStdout(os.Stderr, "tag", "-l", "--points-at", commit)
 	if err != nil {
 		return "", err
 	}
@@ -75,7 +118,7 @@ func gitCommitTag(commit string) (string, error) {
 	return strings.TrimSpace(out), nil
 }
 
-func gitIsDirty(pkg, commit string) (bool, error) {
+func (g git) isDirty(pkg, commit string) (bool, error) {
 	// If it isn't HEAD it can't be dirty
 	if commit != "HEAD" {
 		return false, nil
@@ -86,11 +129,11 @@ func gitIsDirty(pkg, commit string) (bool, error) {
 	// because `git diff-index` only uses the `lstat` result and
 	// not the actual file contents. Running `git update-index
 	// --refresh` updates the cache.
-	if err := gitCommand("update-index", "-q", "--refresh"); err != nil {
+	if err := g.command("update-index", "-q", "--refresh"); err != nil {
 		return false, err
 	}
 
-	err := gitCommand("diff-index", "--quiet", commit, "--", pkg)
+	err := g.command("diff-index", "--quiet", commit, "--", pkg)
 	if err == nil {
 		return false, nil
 	}

src/cmd/linuxkit/pkglib/pkglib.go

@@ -36,6 +36,7 @@ type Pkg struct {
 	hash       string
 	dirty      bool
 	commitHash string
+	git        *git
 }
 
 // NewFromCLI creates a Pkg from a set of CLI arguments. Calls fs.Parse()
@@ -138,20 +139,27 @@ func NewFromCLI(fs *flag.FlagSet, args ...string) (Pkg, error) {
 		}
 	})
 
-	gitDirty, err := gitIsDirty(hashPath, hashCommit)
+	git, err := newGit(pkgPath)
 	if err != nil {
 		return Pkg{}, err
 	}
 
-	dirty = dirty || gitDirty
-
-	if hash == "" {
-		if hash, err = gitTreeHash(hashPath, hashCommit); err != nil {
+	if git != nil {
+		gitDirty, err := git.isDirty(hashPath, hashCommit)
+		if err != nil {
 			return Pkg{}, err
 		}
 
-		if dirty {
-			hash += "-dirty"
+		dirty = dirty || gitDirty
+
+		if hash == "" {
+			if hash, err = git.treeHash(hashPath, hashCommit); err != nil {
+				return Pkg{}, err
+			}
+
+			if dirty {
+				hash += "-dirty"
+			}
 		}
 	}
 
@@ -167,6 +175,7 @@ func NewFromCLI(fs *flag.FlagSet, args ...string) (Pkg, error) {
 		cache:      !pi.DisableCache,
 		dirty:      dirty,
 		pkgPath:    pkgPath,
+		git:        git,
 	}, nil
 }
 
@@ -189,7 +198,11 @@ func (p Pkg) ReleaseTag(release string) (string, error) {
 
 // Tag returns the tag to use for the package
 func (p Pkg) Tag() string {
-	return p.org + "/" + p.image + ":" + p.hash
+	t := p.hash
+	if t == "" {
+		t = "latest"
+	}
+	return p.org + "/" + p.image + ":" + t
 }
 
 // TrustEnabled returns true if trust is enabled