Re: [PATCH] git-submodule.sh: Support 'checkout' as a valid update command

2014/1/7 Junio C Hamano [off-list ref]:

It is not about preference but what we want to convey to the
readers.  When you start the sentence with "Oh, it already works
correctly", the readers need to see this sentence finished: "It
already works, it is handled correctly, but we change the code
nevertheless because ...?".

Here is my attempt to fill that "because ..." part:

        Subject: git-submodule.sh: 'checkout' is a valid update mode

        'checkout' is documented as one of the valid values for
        'submodule.<name>.update' variable, and in a repository with
        the variable set to 'checkout', "git submodule update"
        command do update using the 'checkout' mode.

        However, it has been an accident that the implementation
        works this way; any unknown value would trigger the same
        codepath and update using the 'checkout' mode.

        Tighten the codepath and explicitly list 'checkout' as one
        of the known update modes, and error out when an unknown
        update mode is used.

        Also, teach the codepath that initializes the configuration
        variable from in-tree .gitmodules that 'checkout' is one of
        the valid values---the code since ac1fbbda (submodule: do
        not copy unknown update mode from .gitmodules, 2013-12-02)
        used to treat the value 'checkout' as unknown and mapped it
        to 'none', which made little sense.

I wouldn't be able to explain the change better than your description.
Also, I was under the improper assumption that the change was obvious.
Thank you very much for the amended patch description.

Cheers,
Francesco