Re: [PATCH] branch: make --set-upstream saner without an explicit starting point

Junio C Hamano [off-list ref] writes:

I think it was a mistake that nobody noticed that it is likely that
the operation most often will be done for the current branch and the
usual "give me one branch name to operate on, or I'll operate on the
current branch" command line convention of "git branch" commannd is
not a good fit for it, when "set upstream" feature was added, and
suggested an alternative syntax that avoids the mistake you quoted
above, perhaps something like:

	git branch --set-upstream-to=origin/master [HEAD]

which would have been very clear whose upstream is set to what (with
or without the name of the other branch).  In other words, make the
name "origin/master" *NOT* the first branch name on the command line
in the usual sense, but a parameter to the --set-upstream option, so
that "give me one branch name to operate on, or I'll operate on the
current branch" convention is still kept.

You also broke people who corrected another kind of mistake in this
workflow:
...
Coming from the above observation, while I am sympathetic to your
cause and agree that we would want to do something about it, I am
having a hard time to convince myself that your patch is the best
way to go.

I am not entirely happy with the hypothetical "set-upstream-to"
myself, either.

Thinking about it a bit more, I am starting to think that something
based on the "set upstream to" could be a sane way forward:

 * add "git branch [--set-upstream-to=<name>]" that does what your
   patch does.  The synopsis must make it clear that <name> is not
   the usual first <name> like other "branch" command line arguments
   that specify the branch being operated on, but is an argument to
   the --set-upstream option [*1*].

 * when "git branch --set-upstream <name>" without <start point>
   is given, you first see if <name> exists and find out the
   upstream of <name>, do what the user told you to do (i.e. reset
   the upstream of the <name>d branch to the current branch), and
   give hints to recover.  Two possibilities:

     $ git checkout frotz
     $ git branch --set-upstream xyzzy
     Branch xyzzy set up to track local branch frotz.
     If you wanted to make frotz track xyzzy, do this:
       $ git branch --set-upstream xyzzy <original>
       $ git branch --set-upstream-to xyzzy

     $ git checkout frotz
     $ git branch --set-upstream origin/xyzzy
     Branch origin/xyzzy set up to track local branch frotz.
     If you wanted to make frotz track xyzzy, do this:
       $ git branch -d origin/xyzzy
       $ git branch --set-upstream-to origin/xyzzy

 * possibly, deprecate --set-upstream as a historical wart that had
   misdesigned UI, and when it is used, give deprecation warning and
   nudge the user to use --set-upstream-to instead.


[Footnote]

*1* The parseopt parser will allow both of:

    $ git branch --set-upstream-to=origin/master
    $ git branch --set-upstream-to origin/master

    but the braket around the option name "--set-upstream-to" and
    its argument <name> should make it clear, i.e.

	git branch [--set-upstream-to <name>] [<branch>]

    or

    	git branch [--set-upstream-to=<name>] [<branch>]