[Gnu-arch-users] Re: Star-merge Fatally Wounded

[Stefan Monnier]

> Here is an alternate scenario that does not involve user error:

> Brian:
> % tla get B
> * getting B-1
> % cd B-1
> % tla star-merge A
> * star merging A-1

> Albert:
> % tla get A
> * getting A-1
> % cd A-1
> % tla star-merge B
> * star merging B-1

> Brian:
> % tla commit -s "merged latest A"

> Albert:
> % tla commit -s "merged latest B"

> It is impossible for users to detect and prevent this scenario using Arch.
> They can only do it by communicating out-of-band: "Albert, don't star-merge
> me yet; I'm merging you.",  "Okay, Brian."

You can reduce the race a bit by checking "tla missing <branch>" just before
doing the commit.  I could even imagine `tla commit' doing the
check automatically.

Of course, the race still exists, especially in the presence of mirrors, but
for the case where there is no mirror o where the mirror can be updated
before running `tla missing', the window would be significantly reduced.


        Stefan