Fix relative path finding (#982) (#989)

strings.TrimPrefix can give the wrong result with case-insensitive
paths. filepath.Rel usually works better.

buffalo/cmd/build/archived_assets.go

@@ -6,7 +6,6 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"strings"
 
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -73,7 +72,11 @@ func (b *Builder) buildAssetsArchive() error {
 		}
 
 		if baseDir != "" {
-			header.Name = filepath.Join(baseDir, strings.TrimPrefix(path, source))
+			rel, err := filepath.Rel(source, path)
+			if err != nil {
+				return errors.WithStack(err)
+			}
+			header.Name = filepath.Join(baseDir, rel)
 		}
 
 		if info.IsDir() {

generators/files.go

@@ -70,8 +70,10 @@ func Find(path string) (Files, error) {
 					if info != nil && !info.IsDir() {
 						if filepath.Ext(p) == ".tmpl" {
 							f := File{ReadPath: p}
-							rel := strings.TrimPrefix(p, root)
-
+							rel, err := filepath.Rel(root, p)
+							if err != nil {
+								rel = strings.TrimPrefix(p, root)
+							}
 							paths := strings.Split(rel, string(os.PathSeparator))
 
 							li := len(paths) - 1