Re: [PATCH 5/5] index: offer advice for unknown index extensions

> 
> On Tue, Nov 20 2018, Jonathan Nieder wrote:
> 
> Just commenting here on the end-state of this since it's easier than
> each patch at a time:
> 
> First, do we still need to be doing %.4s instead of just %s? It would be
> easier for translators / to understand what's going on if it were just
> %s. I.e. "this is the extension name" v.s. "this is the first 4 bytes of
> whatever it is...".
> 
>>   			return error("index uses %.4s extension, which we do not understand",
>>   				     ext);
> 
> Missing _(). Not the fault of this series, but something to fix while
> we're at it.
> 
> Also not the fault of this series, the "is this upper case" test is
> unportable, but this is probably the tip of the iceberg for git not
> working on EBCDIC systems.
> 
> This message should say something like "Index uses the mandatory %s
> extension" to clarify and distinguish it from the below. We don't
> understand the upper-case one either, but the important distinction is
> that one is mandatory, and the other can be dropped. The two messages
> should make this clear.
> 
> Also, having advice() for that case is even more valuable since we have
> a hard error at this point. So something like:
> 
>      "This is likely due to the index having been written by a future
>      version of Git. All-lowercase index extensions are mandatory, as
>      opposed to optional all-uppercase ones which we'll drop with a
>      warning if we see them".
> 

>>   		trace_printf("ignoring %.4s extension\n", ext);
>> +		if (advice_unknown_index_extension) {
>> +			warning(_("ignoring optional %.4s index extension"), ext);
> 
> Should start with upper-case. Good that it says "optional".
> 
>> +			advise(_("This is likely due to the file having been written by a newer\n"
>> +				 "version of Git than is reading it. You can upgrade Git to\n"
>> +				 "take advantage of performance improvements from the updated\n"
>> +				 "file format.\n"
> 
> Let's not promise performance improvements with this extension in a
> future version. We have no idea what the extension is, yeah right now
> it's going to be true for the extension that prompted this patch series,
> but may not be in the future. So just something like this for the last
> sentence:
> 
>      You can try upgrading Git to use this new index format.

> 
>> +				 "\n"
>> +				 "Run \"%s\"\n"
>> +				 "to suppress this message."),
>> +			       "git config advice.unknownIndexExtension false");
> 
> Somewhat of an aside, but if I grep:
> 
>      git grep -C10 'git config advice\..*false' -- '*.[ch]'
> 
> There's a few existing examples of this, but the majority of advice()
> messages don't say in the message how you can turn these off. Do we
> think this a message users would especially like to turn off? I have the
> opposite impression, it's a one-off in most cases, although not in the
> case where an editor has an embedded git.
> 
> I think it would make sense to add this sort of thing to the advice()
> API, i.e.:
> 
>      advice_with_config_hint(_("<message>"), "unknownIndexExtension");
> 
> Which would then know how to consistently print this advice about how to
> turn off the warning.
>