[BuildStream] Proposal: More development snapshots, more often

[Chandan Singh <chandan chandansingh net>]

Hi all,

BuildStream 2.0 has been under development for quite some time now.
Over this time, many things have changed - plugins are moving out, we
are in process of gaining and losing various dependencies (buildbox,
fuse etc).

Not providing a good indication for these changes makes it difficult
for anyone trying to follow BuildStream's master. So, I would like to
propose tagging more development snapshots. This would help anyone who
is managing a copy of BuildStream using something like BuildStream (or
BuildStream itself).

Same as the master branch, these snapshots will not come with any sort
of guarantees. They will not be expected to maintain
backwards/forwards compatibility. Also, they will serve merely as a
tagging mechanism. They would _not_ require to be maintained or
patched in future.

I think this is a relatively small workflow change to do. But, it will
make life a bit easier for anyone trying to consume BuildStream's
master. I belive such real-world testing is very important. For
example, we recenly identified a bunch of grpc-related issues when
trying to update our copy of BuildStream. Such issues might be go
uncaught if we don't make it easy for people to test new versions.

For making these snapshots, there doesn't need to be a big ceremony,
other than creating a tag on GitLab. It would be good to do so when
adding/removing any external dependencies, making breaking changes, or
other major changes. This would also give us the ability to
meaningfully reference these points in history, rather than
remembering them by their commit ids.

Additionally, I have noticed some of us already put NEWS entries for
such changes. If we make it a convention to follow this, the NEWS file
will also serve as a handy guide for anyone maintaining their version
of BuildStream.

Let me what you think of the idea. Thanks!

Chandan