Changing default for ~remember~ (was: [RFC] I want to disable submit_branch on my computer for all branches. How can I do that?)

[Stephen J. Turnbull]

Barry Warsaw writes:
 > On May 17, 2011, at 10:39 AM, Ben Finney wrote:
 > 
 > >Oof. I find that the "default to remember on first use" behaviour makes
 > >Bazaar easy to teach.
 >
 > Agreed.  The fact that Mercurial *doesn't* do this was one little pain point
 > in starting to use it.  This is a really nice behavior for Bazaar (IMO).

Hey, are you sure you understand how small a change is being discussed
here?  First, Mercurial doesn't even have --remember options.  Yes,
that's painful.

Second, what Martin and I are talking about is changing the behavior
of *merge* *only*.  The semantics of merge are very often "merge THAT"
(rather than "merge [it again]"), so specifying the branch to merge is
natural in most cases IME, with the single exception of updating from
parent.

But I advocate (and I think Martin does too) that *branch* will still
have "remember parent" semantics, and *push* and *pull* will still
have "remember mirror" semantics (because push and pull have mirror
semantics, it's hard to create a complex mess, so I would argue
there's little harm that can happen), so that

# scaffolding
function addcommit () { echo $1 > $1; bzr add $1; bzr commit -m "add $1"; }

# set up parent repo
pushd /tmp; mkdir a
pushd a; bzr init; addcommit foo; popd

# make a branch
bzr branch a b

#add more content
pushd a; addcommit bar; popd

# OK, what can we do in b?
pushd ../b
bzr merge                # LOOK MA! NO ARGUMENTS!
                         # "Merge from parent" is the default.
addcommit baz
bzr push ../a            # Argument needed.
                         # "Push to parent" is NOT the default.
addcommit quux
bzr push                 # LOOK MA! NO ARGUMENTS!
                         # "Push to last" is magic.
popd

DTRTs.  I would argue that merge from parent is generally a safe
default (typically it's an authoritative repo or mirror thereof),
while specified merge sources are likely to be volatile feature
branches, and you don't want to accidentally merge those.  Similarly,
"push to last" is generally pretty safe I should think, especially if
non-fastforward pushes are denied by the target.  I think this is the
appropriate amount of magic.

OTOH, if you want Doolittle[1] merge semantics, all you need to do is
add

pushd a; bzr merge --remember ../b; popd

to the above, and now you can criss-cross merge to your heart's
content.  I'm not sure that's something you want novices doing, and
it's unlikely to be the way things work for real workflows AFAICS.
But it's available if you want it....

Footnotes: 
[1]  Ringworld puppeteer, aka pushme-pullyou.