Re: fast-import on existing branches

From: Elijah Newren <newren@gmail.com>
Date: Mar 11, 2019, 19:46 UTC
Message-ID: <CABPp-BGs4E48bBQ0e94jxhoXv6t9nzwoNEEnb37tUBpTsi_mCw@mail.gmail.com>
In-Reply-To: <DB6PR8303MB006927B6267629467F783F58FD4D0@DB6PR8303MB0069.EURPRD83.prod.outlook.com>

Hi Norbert,

On Fri, Mar 8, 2019 at 9:38 AM Norbert Nemec <Norbert.Nemec@microsoft.com> wrote:

Show 7 quoted lines

>
> Thanks, Elijah, I had indeed missed that block about the ^0 handling.
>
> I still don't get why this awkward workaround is required. Why isn't that lookup done by default? Performance can't be the reason, since the same lookup is done lateron anyway, just as correctness check. The way I read the documentation, providing no "from" should continue committing to a branch in any case. I would never have seen the continuation of an incremental import a "special case". There is a number of tools around that sync a git repo from some other source and would regularly need to continue an existing branch.
>
> Greetings,
> Norbert

If this "awkward workaround", as you put it, were removed it would make it impossible to create a commit with no parent without using a different branch name. I really like being able to export, modify, and re-import history, using something of the form:

   git fast-export --all | <edit the stream somehow> | git fast-import --force

which would no longer work if fast-import automatically assumed a parent for every from-less commit in the input based on the reference name. Personally, I'm more on the side of not understanding why "from" isn't required whenever you want your commit to have a parent; users can specify either a sha or a mark-id easily enough; I don't see what it saves to allow omitting it, and it inevitably leads to other confusion like yours. But I'm well over a decade too late to advocate for that.

Hope that helps, Elijah