Re: [RFC/PATCH] Add interpret-trailers builtin

[Junio C Hamano <gitster@pobox.com>]

Christian Couder <chriscool@tuxfamily.org> writes:

> From: Junio C Hamano <gitster@pobox.com>
>
>> Christian Couder <christian.couder@gmail.com> writes:
>> 
>>> To append a s-o-b only if there is no s-o-b already, one would need to use:
>>>
>>> [trailer "signoff"]
>>>          key = "Signed-off-by:"
>>>          if_exist = dont_append
>>>          if_missing = append
>>>          command = echo "$GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"'
>> 
>> But that is insufficient to emulate what we do, no?  I.e. append
>> unless the last one is from the same person we are about to add.
>
> Yeah, but, with DONT_REPEAT_PREVIOUS, it would be possible using:
>
> [trailer "signoff"]
>          key = "Signed-off-by:"
>          if_exist = dont_repeat_previous
>          if_missing = append
>          command = echo "$GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"'

Anything is possible, but "possible" does not justify "it is better
way than other possible ways".

What are the plausible values for if_missing?  If if_missing needs
"prepend", for example, in addition to "append", does it mean
if_exist also needs corresponding "prepend" variant for the value
"dont_repeat_previous" you would give to if_exist?

Having two that are seemingly independent configuration does not
seem to be helping in reducing complexity (by keeping settings that
can be independently set orthogonal, by saying "if the other rule
decides to add, do we append, prepend, insert at the middle?", for
example).

How would one differentiate between "there is a field with that key"
and "there is a field with that <key, value> combination" with a
single if_exist?  Add another variable if_exist_exact?