msfr shouldn't swallow os.IsNotExist

- fsrepo calls and checks for this error (`fsrepo.go:140`)

License: MIT
Signed-off-by: Zander Mackie <zmackie@gmail.com>

repo/fsrepo/migrations/mfsr.go

@@ -23,8 +23,8 @@ func (rp RepoPath) Version() (int, error) {
 	}
 
 	fn := rp.VersionFile()
-	if _, err := os.Stat(fn); os.IsNotExist(err) {
-		return 0, VersionFileNotFound(rp)
+	if _, err := os.Stat(fn); err != nil {
+		return 0, err
 	}
 
 	c, err := ioutil.ReadFile(fn)
@@ -53,9 +53,3 @@ func (rp RepoPath) WriteVersion(version int) error {
 	fn := rp.VersionFile()
 	return ioutil.WriteFile(fn, []byte(fmt.Sprintf("%d\n", version)), 0644)
 }
-
-type VersionFileNotFound string
-
-func (v VersionFileNotFound) Error() string {
-	return "no version file in repo at " + string(v)
-}

repo/fsrepo/migrations/mfsr_test.go

@@ -2,6 +2,7 @@ package mfsr
 
 import (
 	"io/ioutil"
+	"os"
 	"testing"
 
 	"github.com/ipfs/go-ipfs/thirdparty/assert"
@@ -21,6 +22,12 @@ func TestVersion(t *testing.T) {
 	_, err := rp.Version()
 	assert.Err(err, t, "Should throw an error when path is bad,")
 
+	rp = RepoPath("/path/to/nowhere")
+	_, err = rp.Version()
+	if !os.IsNotExist(err) {
+		t.Fatalf("Should throw an `IsNotExist` error when file doesn't exist: %v", err)
+	}
+
 	rp = testVersionFile("4", t)
 	_, err = rp.Version()
 	assert.Err(err, t, "Bad VersionFile")