[PATCH 2 of 4] clone to master bookmark if available

[Matt Mackall]

On Fri, 2011-11-04 at 10:42 +0100, arne_bab at web.de wrote:
> # HG changeset patch
> # User Arne Babenhauserheide <bab at draketo.de>
> # Date 1320398369 -3600
> # Node ID 8f614fd777b7190329b9fe705b6e1f518d9193ab
> # Parent  0cc7332a0bb20c3daf003f3fe0a140f5925f0eb8
> clone to master bookmark if available.

(this is not at all the standard commit summary style)

I think making this built-in default behavior is mildly interesting, but
I really don't like the git nomenclature here. The progressive in me has
always winced at master/slave terminology in computing and while this
usage is arguably partly in the sense 'master key', I think it's still
mostly in the sense of 'ruler'. Since I have a say here (unlike in SCSI,
DMA, and SPI specs), I'd prefer to pick something more neutral. (This is
not an invitation to debate or nitpick my politics of language, folks.)

The precedent in Mercurial of course is "default": default path and
default branch. It's obviously a bit problematic to have both a default
branch and a default bookmark since they're both in the lookup
namespace, so perhaps a simple variant of that is needed. We could
perhaps have a notion of the default bookmark on the default branch, ie
default/default'.

Also, I think that there are some other loose ends with bookmarks that
need to be tied up before we get too far thinking about this.

For instance, Alice clones Bob's bookmark B. Alice and Bob both commit
and advance B. Now when Alice pulls, she gets a warning that her B
bookmark is 'divergent'. Now Alice has an extra head but only one
bookmark (her own). This works fine if she now has only two heads on her
branch: merge picks the right one, then B points to the merge and push
pushes it.

But if her current branch already had several heads, 'hg merge' won't
have a default choice, nor will 'hg merge B' do anything useful. She may
end up merging with the wrong head and then push will refuse to move B
on the server. And if B is actually your 'master' concept, things are
now a bit messy.

..which all suggests we need to figure out a nice way to track multiple
bookmarks of the same name first. Git does this with a "namespace"
notion, which is one possibility.

-- 
Mathematics is the supreme nostalgia of our time.