Re: idea: git "came from" tags

From: Michael J Gruber <git@drmicha.warpmail.net>
Date: Jan 18, 2010, 09:49 UTC
Message-ID: <4B542EB2.5030407@drmicha.warpmail.net>
In-Reply-To: <hj0nl9$uds$2@ger.gmane.org>

D Herring venit, vidit, dixit 18.01.2010 05:22:

Show 9 quoted lines

> Actors:
> - public "upstream" repository
> - public "local" repository
> - end users tracking both
> 
> Situation:
> - local starts by tracking upstream
> - local makes changes, commits, and sends upstream
> - users now tracking local ahead of upstream

Here I have to ask why. If users choose to track a volatile branch then they have to live with rebasing or hard resets. If they want something stable then they should track upstream.

Show 7 quoted lines

> - upstream makes modified commits
> - local satisfied, wants to reset master to upstream/master
> 
> Problem:
> - A merge will perpetually leave two parallel branches.  Even though
> there are no longer any diffs, local/master cannot use the same
> objects as upstream/master.

If there are no diffs then, in fact, it can share most objects since most trees will be the same, only a few commit objects will differ.

Show 14 quoted lines

> - A hard reset lets local/master return to sharing objects with
> upstream/master; but this may break pulls or cause other problems for
> users.
> 
> Proposed solution:
> - Local adds a "came from" tag to upstream/master, leaves a tag on the
> head of local/master, and does a hard reset from local/master to
> upstream/master.  When a user tracking local/master does a pull, their
> client detects a non-fast-forward, finds the came-from tag, and treats
> it as a fast-forward.
> 
> Basically, this is a protocol to glue a "strategy ours" merge onto an
> existing tree.  This way local can cleanly track upstream, with no
> added complexity in the nominal (no local changes) case.

But doesn't that mean that users completely trust you about what they should consider a fast forward, i.e. when they should do a hard reset? So, this is completely equivalent to following one of your branches with +f, i.e. having a public a branch which they pull from no matter what, and having a private branch which pushes to the public one in case of fast-forwards as well as in the case when you would use your special tag.

Michael