Re: [PATCH 0/5] Some submodule bugfixes and "reattaching detached HEADs"

From: Stefan Beller <sbeller@google.com>
Date: May 31, 2017, 22:09 UTC
Message-ID: <CAGZ79kYEGQit+7Dqs7ggzRMq9y=pHFhpn-Spk3zVw2ffsc2nXw@mail.gmail.com>
In-Reply-To: <CAGZ79kb52QDUG0RtTXNEEpMJR1CSMYMrRHTRRvGn0-cF=HnzWw@mail.gmail.com>

On Mon, May 1, 2017 at 9:04 PM, Stefan Beller <sbeller@google.com> wrote:

Show 8 quoted lines

>>
>>> I don't know why submodules were originally designed to be in a
>>> detached HEAD state but I much prefer working on branches (as I'm sure
>>> many other developers do) so the prospect of this becoming the norm is
>>> exciting! :D
>>
>
> I'll think about this more.

What the current model is missing is the possibility to have a symbolic link not just to a ref within a repository, but to the outside of a repository (such as the superproject in this case).

So we could have a HEAD with a content like:

    "super: <superprojects git dir> [LF <path inside superproject>]"

Then we would use the HEAD to determine if the superproject would touch a submodule at all. Example workflow:

    git -C <sub> checkout --reattach-to-superproject

    # hack away in the submodule

    # This will make a commit in <sub> and add the
    # resulting object to the index of the superproject
    # because HEAD is tracking the superproject.
    # so in order to have HEAD containing the new
    # commit we have to change the superproject:
    git -C <sub> commit -a -m "message"

    # This has also interesting consequences for
    # submodule related commands:
    git checkout --recurse-submodules <tree-ish>
    # Any submodule whose HEAD is attached to the
    # superproject would be touched, the others would
    # not.

By being directly attached to the superproject, it would be easy to find all submodules that are changed, via a

    git -C <super> status # no need to recurse, even!

The whole "checkout --recurse-submodules" series is based on assumptions of the current mental model of how branches and detached HEADs work.

A submodule would have a symref