osfs: Override the WriteTo interface

The WriteTo signature for osfs.file has been changed so that it
is no longer a io.WriterTo implementation. The built-in implementation
of WriterTo is rather inefficient when coupled with go-git. Further
investigation is required to understand whether this is an upstream
issue or something very specific to osfs.BoundOS + go-git.

Note that this only affects osfs.BoundOS, as ChrootHelper already
ensures that osfs.ChrootOS does not implement io.WriterTo.

Signed-off-by: Paulo Gomes <[email protected]>

Author: pjbgf

osfs/os.go

@@ -6,6 +6,7 @@ package osfs
 
 import (
 	"fmt"
+	"io"
 	"io/fs"
 	"os"
 	"sync"
@@ -109,3 +110,8 @@ type file struct {
 	*os.File
 	m sync.Mutex
 }
+
+func (f *file) WriteTo(w io.Writer) error {
+	_, err := f.File.WriteTo(w)
+	return err
+}