fix(fs): use new OsFS instead of os.DirFS during execution (#1416)

DirFS("/") roots the filesystem. Relative paths are resolved relative
to this root. Paths with a leading `/` are invalid.
Introduced OsFS to use during normal CLI execution, which forwards to
corresponding os package functions.
While still allowing other FS implementations during testing.

Author: cgoetz-inovex

internal/pkg/utils/os_fs.go

@@ -0,0 +1,18 @@
+package utils
+
+import (
+	"io/fs"
+	"os"
+)
+
+var _ fs.ReadFileFS = OsFS{}
+
+type OsFS struct{}
+
+func (o OsFS) Open(name string) (fs.File, error) {
+	return os.Open(name)
+}
+
+func (o OsFS) ReadFile(name string) ([]byte, error) {
+	return os.ReadFile(name)
+}

main.go

@@ -7,6 +7,7 @@ import (
 	"github.com/stackitcloud/stackit-cli/internal/pkg/config"
 	"github.com/stackitcloud/stackit-cli/internal/pkg/print"
 	"github.com/stackitcloud/stackit-cli/internal/pkg/types"
+	"github.com/stackitcloud/stackit-cli/internal/pkg/utils"
 )
 
 // These values are overwritten by GoReleaser at build time
@@ -28,7 +29,7 @@ func main() {
 		Printer:    printer,
 		CliVersion: version,
 		Date:       date,
-		Fs:         os.DirFS("/"),
+		Fs:         utils.OsFS{},
 		Args:       os.Args[1:],
 	}
 	if !cmd.Execute(&params) {