Allow specifying binary path in image

Previously this was hard-coded to `/ko-app/<app-name>`.

go-releaser allows specifying the binary (including directory prefix);
we now support the same.

pkg/build/config.go

@@ -79,14 +79,16 @@ type Config struct {
 	// Env allows setting environment variables for `go build`
 	Env []string `yaml:",omitempty"`
 
+	// Binary allows overriding the output binary name (in the image)
+	Binary string `yaml:",omitempty"`
+
 	// Other GoReleaser fields that are not supported or do not make sense
 	// in the context of ko, for reference or for future use:
 	// Goos         []string    `yaml:",omitempty"`
 	// Goarch       []string    `yaml:",omitempty"`
 	// Goarm        []string    `yaml:",omitempty"`
 	// Gomips       []string    `yaml:",omitempty"`
 	// Targets      []string    `yaml:",omitempty"`
-	// Binary       string      `yaml:",omitempty"`
 	// Lang         string      `yaml:",omitempty"`
 	// Asmflags     StringArray `yaml:",omitempty"`
 	// Gcflags      StringArray `yaml:",omitempty"`

pkg/build/gobuild.go

@@ -496,25 +496,39 @@ func tarBinary(name, binary string, platform *v1.Platform) (*bytes.Buffer, error
 	// For Windows, the layer must contain a Hives/ directory, and the root
 	// of the actual filesystem goes in a Files/ directory.
 	// For Linux, the binary goes into /ko-app/
-	dirs := []string{"ko-app"}
+	appDir := filepath.Dir(name)
+	dirs := []string{appDir}
 	if platform.OS == "windows" {
 		dirs = []string{
 			"Hives",
-			"Files",
-			"Files/ko-app",
+			"Files/" + appDir,
 		}
 		name = "Files" + name
 	}
 	for _, dir := range dirs {
-		if err := tw.WriteHeader(&tar.Header{
-			Name:     dir,
-			Typeflag: tar.TypeDir,
-			// Use a fixed Mode, so that this isn't sensitive to the directory and umask
-			// under which it was created. Additionally, windows can only set 0222,
-			// 0444, or 0666, none of which are executable.
-			Mode: 0555,
-		}); err != nil {
-			return nil, fmt.Errorf("writing dir %q to tar: %w", dir, err)
+		// Create all parent directories also
+		var parents []string
+		current := dir
+		for {
+			parents = append(parents, current)
+			current = filepath.Dir(current)
+			if current == "/" {
+				break
+			}
+		}
+
+		for i := len(parents) - 1; i >= 0; i-- {
+			parent := parents[i]
+			if err := tw.WriteHeader(&tar.Header{
+				Name:     parent,
+				Typeflag: tar.TypeDir,
+				// Use a fixed Mode, so that this isn't sensitive to the directory and umask
+				// under which it was created. Additionally, windows can only set 0222,
+				// 0444, or 0666, none of which are executable.
+				Mode: 0555,
+			}); err != nil {
+				return nil, fmt.Errorf("writing dir %q to tar: %w", parent, err)
+			}
 		}
 	}
 
@@ -789,6 +803,14 @@ func (g *gobuild) configForImportPath(ip string) Config {
 	return config
 }
 
+// pathToWindows converts a unix-style path to a windows-style path.
+// For example, /apps/foo => C:\apps\foo
+func pathToWindows(s string) string {
+	pathComponents := []string{"C:"}
+	pathComponents = append(pathComponents, strings.Split(s, "/")...)
+	return strings.Join(pathComponents, `\`)
+}
+
 func (g *gobuild) buildOne(ctx context.Context, refStr string, base v1.Image, platform *v1.Platform) (oci.SignedImage, error) {
 	if err := g.semaphore.Acquire(ctx, 1); err != nil {
 		return nil, err
@@ -859,9 +881,13 @@ func (g *gobuild) buildOne(ctx context.Context, refStr string, base v1.Image, pl
 		},
 	})
 
-	appDir := "/ko-app"
-	appFileName := appFilename(ref.Path())
-	appPath := path.Join(appDir, appFileName)
+	config := g.configForImportPath(ref.Path())
+	appPath := config.Binary
+	if appPath == "" {
+		appPath = path.Join("/ko-app", appFilename(ref.Path()))
+	}
+	appDir := path.Dir(appPath)
+	appFileName := path.Base(appPath)
 
 	miss := func() (v1.Layer, error) {
 		return buildLayer(appPath, file, platform, layerMediaType)
@@ -900,8 +926,8 @@ func (g *gobuild) buildOne(ctx context.Context, refStr string, base v1.Image, pl
 	cfg.Config.Entrypoint = []string{appPath}
 	cfg.Config.Cmd = nil
 	if platform.OS == "windows" {
-		cfg.Config.Entrypoint = []string{`C:\ko-app\` + appFileName}
-		updatePath(cfg, `C:\ko-app`)
+		cfg.Config.Entrypoint = []string{pathToWindows(appPath)}
+		updatePath(cfg, pathToWindows(filepath.Dir(appPath)))
 		cfg.Config.Env = append(cfg.Config.Env, `KO_DATA_PATH=C:\var\run\ko`)
 	} else {
 		updatePath(cfg, appDir)