Start work on implementing edit-in-kitty in kitty-tool

tools/utils/atomic-write.go

@@ -0,0 +1,55 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package utils
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+var _ = fmt.Print
+
+func AtomicWriteFile(path string, data []byte, perm os.FileMode) (err error) {
+	path, err = filepath.EvalSymlinks(path)
+	if err == nil {
+		path, err = filepath.Abs(path)
+		if err == nil {
+			var f *os.File
+			f, err = os.CreateTemp(filepath.Dir(path), filepath.Base(path))
+			if err == nil {
+				removed := false
+				defer func() {
+					f.Close()
+					if !removed {
+						os.Remove(f.Name())
+					}
+				}()
+				_, err = f.Write(data)
+				if err == nil {
+					err = f.Chmod(perm)
+					if err == nil {
+						err = os.Rename(f.Name(), path)
+						if err == nil {
+							removed = true
+						}
+					}
+				}
+			}
+		}
+	}
+	return
+}
+
+func AtomicUpdateFile(path string, data []byte, perms ...fs.FileMode) (err error) {
+	perm := fs.FileMode(0o666)
+	if len(perms) > 0 {
+		perm = perms[0]
+	}
+	s, err := os.Stat(path)
+	if err == nil {
+		perm = s.Mode().Perm()
+	}
+	return AtomicWriteFile(path, data, perm)
+}