Re: What's cooking in git.git (Jul 2017, #04; Thu, 13)

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Jul 15, 2017, 11:12 UTC
Message-ID: <87iniu2bty.fsf@gmail.com>
In-Reply-To: <xmqqo9snsy0k.fsf@gitster.mtv.corp.google.com>

On Thu, Jul 13 2017, Junio C. Hamano jotted:

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> Here are the topics that have been cooking.  Commits prefixed with
> [...]
>
> * jc/allow-lazy-cas (2017-07-06) 1 commit
>  - push: disable lazy --force-with-lease by default
>
>  Because "git push --force-with-lease[=<ref>]" that relies on the
>  stability of remote-tracking branches is unsafe when something
>  fetches into the repository behind user's back, it is now disabled
>  by default.  A new configuration variable can be used to enable it
>  by users who know what they are doing.  This would pave the way to
>  possibly turn `--force` into `--force-with-lease`.
>
>  Will wait for feedback, then merge to and cook in 'next'.

Aside from the feedback I just sent now 87k23a2d28.fsf@gmail.com, there's my outstanding comment on the config variable name in 877ezkbn6x.fsf@gmail.com which is waiting on your feedback.

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> * sd/branch-copy (2017-06-18) 3 commits
>  - branch: add a --copy (-c) option to go with --move (-m)
>  - branch: add test for -m renaming multiple config sections
>  - config: create a function to format section headers
>
>  "git branch" learned "-c/-C" to create and switch to a new branch
>  by copying an existing one.
>
>  Undecided.
>
>  I personally do not think "branch --copy master backup" while on
>  "master" that switches to "backup" is a good UI, and I *will* say
>  "I told you so" when users complain after we merge this down to
>  'next' and eventually to 'master'.

For anyone following along with this. The reason Sahil & I hacked it up like that is because that's analogous to what the --move option does.

Let's see what *nix does:

    $ rm -rf /tmp/{master,backup}; mkdir /tmp/master && cd /tmp/master && mv /tmp/{master,backup} ; file /tmp/{master,backup}
    /tmp/master: cannot open `/tmp/master' (No such file or directory)
    /tmp/backup: directory

Similarly to that, when you're on "master" "git branch --move backup" could have left you on an orphan branch, but it doesn't, it's the equivalent of "mv && cd" in *nix terms.

So since our --move is really --move-and-checkout I think it would be confusing to introduce a --copy sister option that has the semantics of --copy-no-checkout instead of a corresponding --copy-and-checkout.

I think it's easier to explain & use an option that's "like --move except the old branch doesn't get deleted", which is what this does, instead of "actually not analogous to --move at all".

I happen to want to use this for something where the semantics on that topic work better for me, but I recognize that that's just a matter of taste, if we were green-fielding this I wouldn't mind either way.

But since we're not, and especially with all the confusion around checkout/branch (some of the hairiest UX in git) I think our --move & --copy should be symmetric in the same way that mv(1) an cp(1) are symmetric. Let's not add yet another special case to whether a ref is created/checked out when being manipulated by some mode of checkout/branch.