Comment 1:

Labels changed: added repo-tools, release-none.

Comment 2:

go fmt calls gofmt, which reads the file, reformats it in memory, and then does:
                if *write {
                        err = ioutil.WriteFile(filename, res, 0644)
            if err != nil {
                                return err
                    }
            }
WriteFile is just:
// otherwise WriteFile truncates it before writing.
func WriteFile(filename string, data []byte, perm os.FileMode) error {
        f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
        if err != nil {
                return err
        }
        n, err := f.Write(data)
        if err == nil && n < len(data) {
                err = io.ErrShortWrite
        }
        if err1 := f.Close(); err == nil {
                err = err1
        }
        return err
}
So yes, we're overwriting it in place.  I suppose we could write it to a temp file in
the same dir and then try to automatically rename it into place, at least on Unix (see
Windows issue #8914).  But I think we should make a helper function for that rather than
ask each tool to try to do it.

Status changed to Accepted.

Comment 3:

Perhaps WriteFile should be smart enough and do it for everybody?

CL https://golang.org/cl/33018 mentions this issue.

CL https://golang.org/cl/33020 mentions this issue.

CL https://golang.org/cl/33098 mentions this issue.