Re: [PATCH] push: disable lazy --force-with-lease by default

[lists@haller-berlin.de (Stefan Haller)]

Junio C Hamano <gitster@pobox.com> wrote:

> It turns out that some people use third-party tools that fetch from
> remote and update the remote-tracking branches behind users' back,
> defeating the safety relying on the stability of the remote-tracking
> branches.

Third-party tools are not the only problem. They may make the problem
more likely to occur, but it can also happen without them. (See below.)

> Let's disable the form that relies on the stability of remote-tracking
> branches by default, and allow users who _know_ their remote-tracking
> branches are stable to enable it with a configuration variable.

I'm wondering if people who claim they know they are safe really do.
Elsewhere in the other thread somebody said "I only ever explicitly
fetch, so I know I'm safe". Are you sure?

Consider this example:

$ git checkout the-branch-i-am-collaborating-on-with-my-collegue
$ git pull # make sure I have their latest work
$ git rebase -i ... # do some history rewriting
# OK, so as we need to force-push anyway, let's take the opportunity and
# rebase onto the latest master:
$ git fetch # get latest master
$ git rebase origin/master
$ git push --force-with-lease

This is a very common thing to do at my workplace. And it's unsafe,
because the git fetch may move the remote-tracking branch of the branch
I'm working on.

To make this safe, I guess you'd have to replace "git fetch" with
something like
$ git fetch refs/heads/master:refs/remotes/origin/master

Personally I have never used this form of fetch myself, and I'd be
surprised if any of my coworkers even know it exists.

So know you could decide that _any_ fetch is unsafe, and never use it;
only use git pull. You are still not safe:

$ git checkout the-branch-i-am-collaborating-on-with-my-collegue
$ git pull
$ git rebase -i
# Now another collegue walks in and asks me to look at the regression
# they just introduced on some other branch, so I do
$ git checkout that-other-branch
$ git pull
$ <try to debug their problem>
$ <can't find it either, giving up, shrug>
# go back to what I was doing:
$ git checkout the-branch-i-am-collaborating-on-with-my-collegue
$ git push --force-with-lease

Again, the git pull may have moved the remote-tracking branch of the
branch that I want to force-push. Again, it could be solved by given an
explicit refspec to git pull, but few people ever do this in my
experience, and I certainly never want to.

What I'm getting at is that there's a lot of things that you have to
remember to not do in order to make --force-with-lease without parameter
a useful tool.


-- 
Stefan Haller
Berlin, Germany
http://www.haller-berlin.de/