Re: git interpret-trailers with multiple keys

On Wed, Apr 06, 2016 at 10:28:21PM -0400, Christian Couder wrote:

On Wed, Apr 6, 2016 at 3:30 PM, Michael S. Tsirkin [off-list ref] wrote:

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On Wed, Apr 06, 2016 at 10:42:42AM -0700, Junio C Hamano wrote:

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"Michael S. Tsirkin" [off-list ref] writes:

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On Wed, Apr 06, 2016 at 06:58:30PM +0200, Matthieu Moy wrote:

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"Michael S. Tsirkin" [off-list ref] writes:

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I have this in .git/config

[trailer "r"]
        key = Reviewed-by
        command = "echo \"Michael S. Tsirkin <mst@redhat.com\""
[trailer "s"]
        key = Signed-off-by
        command = "echo \"Michael S. Tsirkin <mst@redhat.com\""

whenever I run git interpret-trailers -t r I see these lines added:

Reviewed-by: Michael S. Tsirkin <mst@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com
Reviewed-by: Michael S. Tsirkin <mst@redhat.com

Why is Reviewed-by repeated?  Bug or feature?

The first two lines are added unconditionally:

$ echo | git interpret-trailers

Reviewed-by: Michael S. Tsirkin <mst@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com

The last line is added because you've asked for it with --trailer r.

Yes, and because the default is to add the trailer at the end.

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I don't think it's currently possible to get the behavior you seem to
expect, ie. to define trailer tokens fully (key and value) in your
config file but use them only on request.

Yes, because you could define for example a function like this:

reviewed() {
    git interpret-trailers --trailer 'Reviewed-by: Michael S. Tsirkin
[off-list ref]' --in-place "$@"
}

So it is kind of easy already to make things requestable.

Not if any commands are configured. interpret-trailers will
insist on running them in any case.

If people really want some configured trailers to be used only on
request, it is possible to add a config option for that.

this is not what the documentation says though:

           If some <token>=<value> arguments are also passed on the
		command line, when a trailer.<token>.command is configured, the
           command will also be executed for each of these arguments.
		And the <value> part of these arguments, if any, will be used to
           replace the $ARG string in the command.

so it says command *for a given token* is run.

I would say that if people really want to run all trailers while also
passing some on command line, *that* should be a config option.
Current default violates the principle of least surprise.

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(BTW, I think you wanted a closing > at the end)

Is this worth fixing? It doesn't look like a behaviour anyone
would want...

CC'ing Christian who's done the "trailers" thing.

Personally, I do not think adding any configured trailers without
being asked is a sensible behaviour, but it is likely that people
already depend on it, as we seem to see "How do I configure to
always add this and that trailer?" from time to time.  I do not
think it is unreasonable to disable the "automatically add
everything that is configured" when the command line arguments ask
for some specific trailer, but I haven't thought deeply about it.

An additional (uninformed) observation is that the 'echo' looks like
an ugly workaround for the lack of "always use this string as the
value" configuration.

Or at least a default.

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Perhaps next to trailer.<token>.command, we
would need trailer.<token>.value?

Yeah, that is possible too.
It could be bit redundant if we already have a config option to say if
the trailer has to be requested.

Seems unrelated - if one just wants a string, using echo as
a command is inefficient and inconvenient.

-- 
MST