Re: [PATCH 1/2] branch: suggest <remote>/<branch> on upstream slip

[Junio C Hamano <gitster@pobox.com>]

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

> "Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
>> From: Harald Nordgren <haraldnordgren@gmail.com>
>>
>> "git branch --set-upstream-to origin main" reads the trailing word as
>> the local branch to operate on and dies with "branch 'main' does not
>> exist", pointing at the wrong problem.
>
> When 'main' does not exist locally,
>
>     $ git branch --set-upstream-to "$anything" main
>
> would fail before even looking at the "$anything" (which is supposed
> to specify the new_upstream for the named local branch 'main').  The
> operation is to set the upstream for 'main', and if 'main' does not
> exist, doesn't the user deserve the error that says 'main' does not
> exist, no matter what "$anything" is, whether it is a well-formed or
> ill-formed remote tracking branch name?
>
> So it is unclear, at least to me, why "branch 'main' does not exist"
> is an inappropriate message, mostly because these three lines does
> not clearly tell me what the user _expected_ the command line to do.

After pondering on this a bit, I _think_ (but I am guessing, and
your job as an author of proposed commit log message is to make sure
your readers do not have to guess) what the user expected was to set
the upstream for the currrent branch.

    When trying to set the upstream for the current branch to "main"
    branch of the remote "origin", i.e.,

        $ git branch --set-upstream-to origin/main

    it is easy for some users to mistakenly say

        $ git branch --set-upstream-to origin main

    But it is a request to set the upstream for the local branch
    "main" to "origin", which is not expected to work as the
    upstream most likely would look like <remote>/<branch> (e.g.,
    "origin/main").  The user would get either one of these errors:

        fatal: branch 'main' does not exist
        fatal: the requested upstream branch 'origin' does not exist

    Give a hint that we _suspect_ the user may have meant to set the
    upstream of the current branch to 'origin/main' (but do so only
    when 'origin/main' does exist), and tell them the right way to
    spell that request.

or something perhaps?