Re: [PATCH 1/5] bisect: read bisect paths with strbuf_getline()

From: Junio C Hamano <gitster@pobox.com>
Date: Feb 15, 2016, 05:05 UTC
Message-ID: <xmqqtwlar2bd.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <56C0EB3F.90202@moritzneeb.de>

Moritz Neeb <lists@moritzneeb.de> writes:

Show 13 quoted lines

>> You would also want to think about the necessity of strbuf_trim()
>> here.  Now strbuf_getline() would trim the trailing CR, would we
>> still need to call strbuf_trim() here?  The code will break if you
>> just remove the call, but on the other hand, you will realize that
>> the trimming done by calling it is excessive and unnecessary, once
>> you inspect the code and learn who writes the file being read here
>> and how.
>
> I am not sure what you mean by excessive: How much can I assume that
> the input is like expected? The files we are talking about are supposed
> to be read and written by git only. But could be modified in theory with
> an editor, right? Then things could break, right? This question maybe holds
> true for the other patches as well, I still have to look into them.

These are all good questions you as a Git contributor to be asking yourself, and I really like the fact that you are thinking aloud here.

As to bisect pathspec, while I do not think it is sensible to change it in the middle of bisection, I do not think it would cause the bisect command to produce an incorrect result if you did so. You would be changing the definition of what is the "middle point" of the history on the fly by changing the pathspec, hence you may end up making the bisection suboptimal, but it shouldn't affect the correctness of the bisection.

So I tend to agree with you that it is a good idea to be prepared to parse what the end user may have futzed with the editor, as long as the user did not break the syntax of the quoted string.

Your answer to the question quoted at the top of this message could be a summary of the above reasoning, with a conclusion: "we would want to tolerate trailing (or leading) whitespaces the user might add with his editor; even though we use strbuf_getline() to remove the CR at the end of line, we still need to strbuf_trim() the line we read".

	Side note: of course, you can instead say "while it is
	technically possible, we have never advertised this file to
	be editable by user, or encouraged them to do so" and
	tighten the parsing to assume only what we write out,
	erroring out when we see any attempt to edit it.

Either way, the most important thing is to record the reasoning behind the design choice you made clearly in the proposed commit log message.

Thanks.