From: Isabella Stephens <istephens@atlassian.com>
Date: Fri, 27 Apr 2018 04:15:53 GMT
Subject: Re: [PATCH v4 1/2] blame: prevent error if range ends past end of file
Message-ID: <dee9083d-0745-6b98-fe5e-fc19d2a5bb9a@atlassian.com>
In-Reply-To: <xmqq36zh1jtj.fsf@gitster-ct.c.googlers.com>

> Maybe I misread the previous discussion and/or your cover letter,
> but I have been assuming that you are trying to avoid failing the
> command in a useless way (e.g. when the file has only ~800 lines but
> the user does not know exactly how many, instead of letting -L1,820 
> to fail with "the file only has 815 lines", pretend that the -L1,815
> was given) and instead give a reasonable fall-back behaviour.

That's correct. In doing so I picked up on a few extra cases where the
behaviour wasn't intuitive, so I've attempted to fix all of those with
this patch. 

> And to be consistent with that world view, I would have expected
> that the meaning of -L<something>,-20 to be updated from "fail if
> <something> is before line #20, or show 20 lines leading to
> <something>" to "show lines leading to <something>, up to 20 lines
> but it is OK if there aren't enough lines in the file to show that
> many".

This is the existing behaviour. -L10,-20 for example will blame the
first 10 lines of a file, it will not fail. My patch doesn't change
this. The case I am discussing is -L,-20 which at the moment blames
the first line of the file. Trying to go backwards from the start of
a file should be considered invalid, in my opinion, however I don't
feel strongly about it - I don't expect this case is common in 
practice.