Re: misleading message printed when worktree add fails

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Nov 28, 2021, 17:00 UTC
Message-ID: <CAPig+cTGq-10ZTBts2LXRVdPMf2vNMX8HTuhg_+ZHSiLX-brOQ@mail.gmail.com>
In-Reply-To: <CA+34VNJbOHYhYgN+p7EsGiRAzf+aAQGeMxCzG1dizFjDRVQVbg@mail.gmail.com>

[please comment inline on this list rather than top-posting]

On Sun, Nov 28, 2021 at 11:47 AM Baruch Burstein <bmburstein@gmail.com> wrote:

Show 14 quoted lines

> > When I perform these actions, I see a "fatal error" message which
> > clearly indicates failure, not success:
> >
> >     % git worktree add ../foo bar
> >     Preparing worktree (checking out 'bar')
> >     fatal: 'bar' is already checked out at '.../wherever'
>
> I see them in the other order:
>
>     fatal: 'master' is already checked out at 'C:/Users/bmbur/temp'
>     Preparing worktree (checking out 'master')
>
> which I understood as "there was an error, but we managed to recover
> somehow and set up the worktree anyway"

Okay, that's happening because the "Preparing" message is sent to stdout, whereas the "fatal" error is sent to stderr, and the streams are being flushed on Windows in a different order than what we typically see on Unix platforms even though the "Preparing" message is actually output first by the code.

A general fix (not specific to git-worktree) might be to have die() (or maybe vreportf()?) flush stdout before reporting the error message on stderr. That should make output order more predictable, such that general status messages appear before error messages.