Re: [PATCH 3/3] shortlog: do not accept revisions when run outside repo

From: Martin Ågren <martin.agren@gmail.com>
Date: Mar 13, 2018, 20:47 UTC
Message-ID: <CAN0heSoP1oVWH0YAFNcL5LG_K7TsmKMAHUA_TiDacVdPtWjTZw@mail.gmail.com>
In-Reply-To: <20180313195640.GA147135@aiede.svl.corp.google.com>

On 13 March 2018 at 20:56, Jonathan Nieder <jrnieder@gmail.com> wrote:

Show 11 quoted lines

> Hi,
>
> Martin Ågren wrote:
>
>>                                                       (So yes, after
>> this patch, we will still silently ignore stdin for confused usage such
>> as `git log v2.15.0.. | git shortlog v2.16.0..`. But at least that does
>> not crash.)
>
> I don't follow here.  Are you saying this command should notice that
> there is input in stdin?  How would it notice?

I have no idea how it would notice (portably!) and the gain seems minimal. I added this to keep the reader from wondering "but wait a minute, doesn't that mean that we fail to catch this bad usage if we're in a repo?". So my answer would be "yep, but it's not a huge problem". Of course, my attempt to pre-emptively answer a question only provoked another one. :-) I could phrase this better.

Show 9 quoted lines

>> --- a/builtin/shortlog.c
>> +++ b/builtin/shortlog.c
>> @@ -293,6 +293,12 @@ int cmd_shortlog(int argc, const char **argv, const char *prefix)
>>  parse_done:
>>       argc = parse_options_end(&ctx);
>>
>> +     if (nongit && argc != 1) {
>
> Just curious: would argc ever be 0 here?  'argc <= 1' might be clearer.

Hmm, good point. It "shouldn't" be 0, but I guess it's better to be safe than sorry. (We seem to have both constructs, in various places.)

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>> +             error(_("no revisions can be given when running "
>> +                     "from outside a repository"));
>> +             usage_with_options(shortlog_usage, options);
>> +     }
>> +
>
> The error message is
>
>         error: no revisions can be given when running from outside a repository
>         usage: ...
>
> Do we need to dump usage here?  I wonder if a simple die() call would
> be easier for the user to act on.

I can see an argument for "dumping the usage makes the error harder than necessary to find". I mainly went for consistency. This ties into your other observations below: what little consistency do we have and in which direction do we want to push it...

Show 9 quoted lines

> Not about this patch: I was a little surprised to see 'error:' instead
> of 'usage:' or 'fatal:'.  It turns out git is pretty inconsistent
> about that: e.g. there is
>
>         error(_("no remote specified"));
>         usage_with_options(builtin_remote_setbranches_usage, options);
>
> Some other callers just use usage_with_options without describing the
> error.

The other two approaches ("die" and "error and usage") can be argued for, but this one ("give usage") just seems wrong to me. I haven't looked for such a place in the code, and maybe they're "obvious", but it seems odd to just give the usage without any sort of hint about what was wrong.

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>  check-attr has a private error_with_usage() helper to implement
> the error() followed by usage_with_options() idiom.  Most callers just
> use die(), like
>
>         die(_("'%s' cannot be used with %s"), "--merge", "--patch");
>
> Documentation/technical/api-error-handling.txt says
>
>  - `usage` is for errors in command line usage.  After printing its
>    message, it exits with status 129.  (See also `usage_with_options`
>    in the link:api-parse-options.html[parse-options API].)
>
> which is not prescriptive enough to help.

I think it would be a larger project to make these consistent. The one I'm adding here is at least consistent with the other one in this file.

> Separate from that, I wonder if the error message can be made a little
> shorter and clearer.  E.g.
>
>         fatal: shortlog <revs> can only be used inside a git repository

Some grepping suggests we do not usually name the command ("shortlog ..."), perhaps to play well with aliasing, nor do we use "such <syntax>" very often, but it does happen. Quoting and allowing for options might make this more correct, but perhaps less readable: "'shortlog [...] <revs>' can only ...". Slightly better than what I had, "revisions can only be given inside a git repository" would avoid some negating.

> Thanks and hope that helps,

It does indeed. I'll give this another 24h and see what I come up with. I believe it will end up in a change to "<= 1", an improved error message and a clearer last few words in the commit message.

Martin