New file change cannot be displayed after e89dbd8f

[gadfly3173]

ExitCode is 1.

[gadfly3173]

I think the judgment of ExitCode in this section is incorrect for the Diff command. Git may use exitcode=1 to indicate changes exist.

sourcegit/src/Commands/Diff.cs

Lines 38 to 43 in a97f163

	var rs = ReadToEnd();
	if (!rs.IsSuccess)
	{
	_result.TextDiff = null;
	return _result;
	}

[love-linger]

如果指定了--exit-code，1代表有差异，0代表没有差异。
代码中并没有指定，并且对于modified文件来说，返回值为0，所以我这里直接忽略了该返回值。