Re: [RFC v2] submodule: Respect requested branch on all clones

On Tue, Jan 07, 2014 at 10:15:25AM -0800, Junio C Hamano wrote:

    submodule: respect requested branch on all clones

    The previous code only checked out the requested branch in cmd_add
    but not in cmd_update; this left the user on a detached HEAD after
    an update initially cloned, and subsequent updates using rebase or
    merge mode will kept the HEAD detached, unless the user moved to the
    desired branch himself.

    Move the branch-checkout logic into module_clone, where it can be
    shared by cmd_add and cmd_update.  Also update the initial checkout
    command to use 'rebase' to preserve branches setup during
    module_clone.  This way, unless the user explicitly asks to work on
    a detached HEAD, subsequent updates all happen on the specified
    branch, which matches the end-user expectation much better.

This looks reasonable to me, but there are still changes I'd like to
make for a v3 (e.g. using submodule.<name>.update to trigger local
branch checkout).  However, I'm currently leaning towards a new 'git
submodule checkout' command with explicit preferred local submodule
branches (see [1]).  Maybe this should all wait until Jens rolls out
his update implementation [2]?

Having writing all the above and then looking at the patch again, it
is not immediately obvious to me where you use "rebase" when doing
the initial checkout, though.

It's used to shift the local branch reference from from the
(arbitrary) cloned remote branch tip to the explicit submodule $sha1.
Otherwise the default method for that operation is a HEAD-detaching
'checkout'. I tried to explain it here [3].

"W. Trevor King" [off-list ref] writes:

quoted

The current Documentation/git-submodule.txt has:

  update::
    Update the registered submodules, i.e. clone missing submodules
    and checkout the commit specified in the index of the containing
    repository.  This will make the submodules HEAD be detached unless
    `--rebase` or `--merge` is specified or the key
    `submodule.$name.update` is set to `rebase`, `merge` or `none`.

Side note but doesn't Francesco's "'checkout' is a valid update mode"
need to update this part of the documentation as well?

That would be nice.  I don't think his patch changes the docs, and I
don't know if mentioning the --checkout option belongs in that patch
as well, or in a separate fixup ;).

Cheers,
Trevor

[1]: http://article.gmane.org/gmane.comp.version-control.git/240097
[2]: http://article.gmane.org/gmane.comp.version-control.git/240117
[3]: http://article.gmane.org/gmane.comp.version-control.git/239953

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