Re: [PATCH 2/2] checkout: introduce "--to-branch" option

On Sun, Dec 12 2021, Junio C Hamano wrote:

ZheNing Hu [off-list ref] writes:

quoted

quoted

It is unclear if you mean "dev1" exactly point at the commit tagged
as v1.1, or you want the branch "dev1" that is a descedanant of
v1.1.  Without telling that to the reader, the above explanation is
useless.

I meant the former.

quoted

And whether you meant the former or the latter, neither use case does
not make much sense.
...
So, "--to-branch v1.1" that finds and checks out a branch whose tip
exactly points at v1.1 would be pretty useless.

...
"git branch --contains v1.1" can find all branches whose history contains the
 commit tagged as v1.1. So what if "git checkout --contains v1.1"?

I already said, whether you meant "the only branch that points
exactly at" or "the only branch that contains", the feature does not
make sense.  Forcing users to keep only a single branch that either
points at a given tag is simply impossible and also useless.  Once
the branch gains even a single commit, it will no loger be pointing
at the tag, so "let's prepare a branch pointing at v1.1 just in case
when I want to start working from there" would not be a good
workflow to begin with.  Forcing users to keep only a single branch
that contains a given tag would encourage even a worse workflow to
throw in unrelated things, whose only commonality is that they all
want to fork from a single tag, into a single branch.

IOW, there is nothing we want to add to "git checkout/switch" for
this topic.  "git checkout --contains $tag" smells like a solution
looking for a problem.

I don't see how it's fundimentally different than the DWIM logic of
taking "<name>" and seeing that there's only one "refs/heads/<name>",
and giving up in other cases where we get ambiguous reference names that
we can't resolve.

I.e. I think this is probably useful for some, it's a common workflow to
have a 1=1 relationship like this, and if it's 1=many we can just handle
it as we do with ambiguous ref, or ambiguous short OIDs for that matter.

But as I noted upthread I really don't see this making sense as a
per-command thing, as opposed to some extension of the "peel"
syntax. I.e. we should (or at least expose it as such to the user)
interpret that sort of argument/newx syntax before "git checkout" et al
get to it, so from a UX perspective you could feed a ^{oid2ref} (or
whatever it would be called) to rev-parse, checkout etc. etc.