Re: [PATCH v3 23/23] checkout: retire --ignore-other-worktrees in favor of --force

On Mon, Jul 6, 2015 at 3:40 PM, Junio C Hamano [off-list ref] wrote:

Eric Sunshine [off-list ref] writes:

quoted

As a safeguard, checking out a branch already checked out by a different
worktree is disallowed. This behavior can be overridden with
--ignore-other-worktrees, however, this option is neither obvious nor
particularly discoverable. As a common safeguard override, --force is
more likely to come to mind. Therefore, overload it to also suppress the
check for a branch already checked out elsewhere.

I hate to be asking this again but why is it a good idea to allow
'ignore-other-worktrees' in the first place (let alone making it
more discoverable)?  You'll have multiple working trees, either
using the new "git worktree" or using the old contrib/workdir, for
one of the two reasons:

 * You need a separate work area to build a new history.

 * You need a separate work area to expand the contents of a
   specific commit.

Here "create binary by running make" falls into the latter category;
as far as Git is concerned, you are only looking at, not extending
the history of any specific branch.

If you are extending the history of some branch, then you would want
to be on that branch.  Why would you want to have another worktree
that will get into a confusing state once you create that commit on
the checked out branch in this newly created worktree?

Wasn't the whole point of making the primary repository aware of the
secondary worktrees via the "linked checkout" mechanism because that
confusion was the biggest sore point of the old contrib/workdir
implementation?

Having never used contrib/get-new-workdir, and not being involved in
the choice, nor recall seeing justification for disallowing the a
branch to be checked out in multiple locations, I lack insight to
answer. I do recall Mark pointing out that this restriction posed a
barrier for his migration from git-new-workdir to "git checkout
--to"[1], and Duy adding --ignore-other-worktrees in response. Mark
presented a use-case here [2], but then the discussion petered out.

I likewise probably lack understanding of the finer points to make a
cogent argument for or against.

[1]: http://thread.gmane.org/gmane.comp.version-control.git/260387/focus=260411
[2]: http://article.gmane.org/gmane.comp.version-control.git/260645