Re: Worktree creation race

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Feb 1, 2019, 19:54 UTC
Message-ID: <CAPig+cRg5E=_QuUz4j4sGNR=ziHth0Lv7hncm_hvZboBvv+bnQ@mail.gmail.com>
In-Reply-To: <20190201131659.GA30564@ash>

On Fri, Feb 1, 2019 at 8:17 AM Duy Nguyen <pclouds@gmail.com> wrote:

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> I'm not going to bother you with code yet (although if you want, you
> can check out branch worktree-name on my gitlab repo), but this is
> what the user facing changes look like. Looking good?
>
> -- 8< --
> diff --git a/Documentation/git-worktree.txt b/Documentation/git-worktree.txt
> @@ -9,7 +9,7 @@ git-worktree - Manage multiple working trees
>  SYNOPSIS
> +'git worktree add' [-f] [--detach] [--checkout] [--lock] [-b <new-branch>] [--name <name>] <path> [<commit-ish>]
> @@ -195,6 +195,13 @@ This can also be set up as the default behaviour by using the
> +--name <name>::
> +       Name of the working tree. Each working tree must have a unique
> +       name. This is also the directory name containing all working
> +       tree's specific information under `$GIT_COMMON_DIR/worktrees`.
> +       If `--name` is not given, the name is based on basename(3)
> +       optionally with a number suffix to make it unique.

I think the "DETAILS" section also needs to be updated. It presently says:

    The private sub-directory’s name is usually the base name of the
    linked working tree’s path, possibly appended with a number to
    make it unique.

Perhaps amend it to:

    ...to make it unique, or the name provided by `--name`.

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>  Porcelain Format
>  ~~~~~~~~~~~~~~~~
>  The porcelain format has a line per attribute.  Attributes are listed with a
> @@ -341,10 +352,12 @@ $ git worktree list --porcelain
>  worktree /path/to/bare-source
>  bare
>
> +name linked
>  worktree /path/to/linked-worktree
>  HEAD abcd1234abcd1234abcd1234abcd1234abcd1234
>  branch refs/heads/master
>
> +name other
>  worktree /path/to/other-linked-worktree
>  HEAD 1234abc1234abc1234abc1234abc1234abc1234a
>  detached

Unfortunately, this will likely break existing tools. When I had outlined the proposed porcelain format, my suggestion was that a "worktree" line would indicate the start of a new stanza (with no blank line), however, as it eventually got implemented (not by me), that recommendation wasn't quite followed. Instead, what has been documented "officially" in the git-worktree man-page is that each stanza will start with a "worktree" line and that there will be a blank line between stanzas. So, the new "name" line will need to be placed somewhere after the "worktree" line in order to avoid tool breakage.