Simple approach to finding project root dir

main.go

@@ -8,8 +8,12 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"path/filepath"
 )
 
+const ManifestName = "manifest.json"
+const LockName = "lock.json"
+
 func main() {
 	flag.Parse()
 
@@ -186,3 +190,41 @@ var getCmd = &command{
 		-vendor	(?) get to workspace or vendor directory
 	`,
 }
+
+func findProjectRootFromWD() (string, error) {
+	path, err := os.Getwd()
+	if err != nil {
+		return "", fmt.Errorf("could not get working directory: %s", err)
+	}
+	return findProjectRoot(path)
+}
+
+func findProjectRoot(from string) (string, error) {
+	var f func(string) (string, error)
+	f = func(dir string) (string, error) {
+
+		fullpath := filepath.Join(dir, ManifestName)
+
+		if _, err := os.Stat(fullpath); err == nil {
+			return dir, nil
+		} else if !os.IsNotExist(err) {
+			// Some err other than non-existence - return that out
+			return "", err
+		}
+
+		base := filepath.Dir(dir)
+		if base == dir {
+			return "", fmt.Errorf("cannot resolve parent of %s", base)
+		}
+
+		return f(base)
+	}
+
+	path, err := f(from)
+	if err != nil {
+		return "", fmt.Errorf("error while searching for manifest: %s", err)
+	} else if path == "" {
+		return "", fmt.Errorf("could not find manifest in any parent of %s", from)
+	}
+	return path, nil
+}

main_test.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestFindRoot(t *testing.T) {
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expect := filepath.Join(wd, "_testdata", "rootfind")
+
+	got1, err := findProjectRoot(expect)
+	if err != nil {
+		t.Errorf("Unexpected error while finding root: %s", err)
+	} else if expect != got1 {
+		t.Errorf("findProjectRoot directly on root dir should have found %s, got %s", expect, got1)
+	}
+
+	got2, err := findProjectRoot(filepath.Join(expect, "subdir"))
+	if err != nil {
+		t.Errorf("Unexpected error while finding root: %s", err)
+	} else if expect != got2 {
+		t.Errorf("findProjectRoot on subdir should have found %s, got %s", expect, got2)
+	}
+
+	got3, err := findProjectRoot(filepath.Join(expect, "nonexistent"))
+	if err != nil {
+		t.Errorf("Unexpected error while finding root: %s", err)
+	} else if expect != got3 {
+		t.Errorf("findProjectRoot on nonexistent subdir should still work and give %s, got %s", expect, got3)
+	}
+
+	got4, err := findProjectRoot(filepath.Join(expect, ManifestName))
+	if err == nil {
+		t.Errorf("Should have err'd when trying subdir of file, but returned %s", got4)
+	}
+}