A perfect and easy way: Override the EditText's onTextContextMenuItem and intercept the android.R.id.paste to be android.R.id.pasteAsPlainText
@Override
public boolean onTextContextMenuItem(int id) {
    if (id == android.R.id.paste) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            id = android.R.id.pasteAsPlainText;
        } else {
            onInterceptClipDataToPlainText();
        }
    }
    return super.onTextContextMenuItem(id);
}
private void onInterceptClipDataToPlainText() {
    ClipboardManager clipboard = (ClipboardManager) getContext()
        .getSystemService(Context.CLIPBOARD_SERVICE);
    ClipData clip = clipboard.getPrimaryClip();
    if (clip != null) {
        for (int i = 0; i < clip.getItemCount(); i++) {
            final CharSequence paste;
            // Get an item as text and remove all spans by toString().
            final CharSequence text = clip.getItemAt(i).coerceToText(getContext());
            paste = (text instanceof Spanned) ? text.toString() : text;
            if (paste != null) {
                ClipBoards.copyToClipBoard(getContext(), paste);
            }
        }
    }
}
And the copyToClipBoard: 
public class ClipBoards {
    public static void copyToClipBoard(@NonNull Context context, @NonNull CharSequence text) {
        ClipData clipData = ClipData.newPlainText("rebase_copy", text);
        ClipboardManager manager = (ClipboardManager) context
            .getSystemService(Context.CLIPBOARD_SERVICE);
        manager.setPrimaryClip(clipData);
    }
}