From: Anders Waldenborg <anders@0x63.nu>
Date: Mon, 27 Jul 2020 22:17:39 GMT
Subject: Re: Questions about trailer configuration semantics
Message-ID: <878sf4r4au.fsf@0x63.nu>
In-Reply-To: <xmqqk0yog1lg.fsf@gitster.c.googlers.com>


Junio C Hamano writes:

> Christian Couder <christian.couder@gmail.com> writes:
>> Yeah, in this case we are not sure if "Acked" or "aCKed" is the right
>> way to spell it.
>
> OK, so in short, the trailer subsystem matches the second level of
> the configuration variable name (e.g. "Acked") in a case insensitive
> way

From what I can understand it tries to match *both* on the second level
AND the value of .key (trailers.c:token_matches_item)

$ printf '\na: 1\nb: 2\nc: 3\n' | \
  git -c 'trailer.A.key=B' interpret-trailers
B: 1
B: 2
c: 3

and then uses the .key value when outputting the result (by calling
trailer.c:token_from_item)

I.e:
it gets "a: 1", tries to find configuration for that, and finds
trailer.A because "a" (case insenitively) matches conf.name, therefore
it outputs value of trailer.A.key + separator + "1"

then it gets "b: 1", and again finds trailer.A because "b" matches
conf.key.

> , and it does *not* normalize the case in the output.  The .key
> request is a mechanism to replace the matched key with the specified
> string, so there is *NO* case normalization in what Anders observed.

Hmm. Maybe the "matching" vs "outputting" makes it clearer.


Given configuration trailer.<NAME>.key=<KEY>

When printing a parsed trailer, e.g from pretty format "%(trailers)",
"git interpret-trailers" passthrough of existing trailers or addition of
a new trailer with --trailer: <KEY> is used in output. If <KEY> is not
configured the trailer token is output the same way as it was in input.

When finding a trailer, e.g for '--trailer x=y' or
trailer.<NAME>.where=before/after: matching is done against both
<NAME> and <KEY>.

When showing a single trailer with pretty format '%(trailers:key=X)' it
is matched against <KEY> only. (I guess one can see this as matching on
the formatted output).


> In other words,
>
>   $ printf '\naCKed: Zz\n' | \
>     git -c 'trailer.Acked.key=Rejected' interpret-trailers --parse
>
> would have emitted "Rejected: Zz".

Indeed.