Resolve symlinked PWD in FileDetector.Detect

When a relative symlink is provided for the pwd in FileDetector.Detect,
it can result in an invalid URL relative to the file root, e.g.
`file:///../modules/foo`. Resolve the absolute path after reading a
symlink in Detect.

detect_file.go

@@ -36,6 +36,13 @@ func (d *FileDetector) Detect(src, pwd string) (string, bool, error) {
 				if err != nil {
 					return "", true, err
 				}
+
+				// The symlink itself might be a relative path, so we have to
+				// resolve this to have a correctly rooted URL.
+				pwd, err = filepath.Abs(pwd)
+				if err != nil {
+					return "", true, err
+				}
 			}
 		}
 

detect_file_unix_test.go

@@ -0,0 +1,70 @@
+// +build test unix
+
+package getter
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// If a relative symlink is passed in as the pwd to Detect, the resulting URL
+// can have an invalid path.
+func TestFileDetector_relativeSymlink(t *testing.T) {
+	tmpDir, err := ioutil.TempDir("", "go-getter")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer os.RemoveAll(tmpDir)
+
+	// We may have a symlinked tmp dir,
+	// e.g. OSX uses /var -> /private/var
+	tmpDir, err = filepath.EvalSymlinks(tmpDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = os.Mkdir(filepath.Join(tmpDir, "realPWD"), 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	subdir := filepath.Join(tmpDir, "subdir")
+	err = os.Mkdir(subdir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	prevDir, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chdir(prevDir)
+
+	err = os.Chdir(subdir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = os.Symlink("../realPWD", "linkedPWD")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// if detech doesn't fully resolve the pwd symlink, the output will be the
+	// invalid path: "file:///../modules/foo"
+	f := new(FileDetector)
+	out, ok, err := f.Detect("../modules/foo", "./linkedPWD")
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if !ok {
+		t.Fatal("not ok")
+	}
+	if out != "file://"+filepath.Join(tmpDir, "modules/foo") {
+		t.Logf("expected: %v", "file://"+filepath.Join(tmpDir, "modules/foo"))
+		t.Fatalf("bad:      %v", out)
+	}
+}