Migrate to go-git/go-git v5.0.0 (#10735)

vendor/github.com/go-git/go-billy/v5/osfs/os_plan9.go

@@ -0,0 +1,83 @@
+package osfs
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"syscall"
+)
+
+func (f *file) Lock() error {
+	// Plan 9 uses a mode bit instead of explicit lock/unlock syscalls.
+	//
+	// Per http://man.cat-v.org/plan_9/5/stat: “Exclusive use files may be open
+	// for I/O by only one fid at a time across all clients of the server. If a
+	// second open is attempted, it draws an error.”
+	//
+	// There is no obvious way to implement this function using the exclusive use bit.
+	// See https://golang.org/src/cmd/go/internal/lockedfile/lockedfile_plan9.go
+	// for how file locking is done by the go tool on Plan 9.
+	return nil
+}
+
+func (f *file) Unlock() error {
+	return nil
+}
+
+func rename(from, to string) error {
+	// If from and to are in different directories, copy the file
+	// since Plan 9 does not support cross-directory rename.
+	if filepath.Dir(from) != filepath.Dir(to) {
+		fi, err := os.Stat(from)
+		if err != nil {
+			return &os.LinkError{"rename", from, to, err}
+		}
+		if fi.Mode().IsDir() {
+			return &os.LinkError{"rename", from, to, syscall.EISDIR}
+		}
+		fromFile, err := os.Open(from)
+		if err != nil {
+			return &os.LinkError{"rename", from, to, err}
+		}
+		toFile, err := os.OpenFile(to, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, fi.Mode())
+		if err != nil {
+			return &os.LinkError{"rename", from, to, err}
+		}
+		_, err = io.Copy(toFile, fromFile)
+		if err != nil {
+			return &os.LinkError{"rename", from, to, err}
+		}
+
+		// Copy mtime and mode from original file.
+		// We need only one syscall if we avoid os.Chmod and os.Chtimes.
+		dir := fi.Sys().(*syscall.Dir)
+		var d syscall.Dir
+		d.Null()
+		d.Mtime = dir.Mtime
+		d.Mode = dir.Mode
+		if err = dirwstat(to, &d); err != nil {
+			return &os.LinkError{"rename", from, to, err}
+		}
+
+		// Remove original file.
+		err = os.Remove(from)
+		if err != nil {
+			return &os.LinkError{"rename", from, to, err}
+		}
+		return nil
+	}
+	return os.Rename(from, to)
+}
+
+func dirwstat(name string, d *syscall.Dir) error {
+	var buf [syscall.STATFIXLEN]byte
+
+	n, err := d.Marshal(buf[:])
+	if err != nil {
+		return &os.PathError{"dirwstat", name, err}
+	}
+	if err = syscall.Wstat(name, buf[:n]); err != nil {
+		return &os.PathError{"dirwstat", name, err}
+	}
+	return nil
+}