zsh_completion: add -b/--branch and -B/--bookmark(s) flags properly
_hg_branch_bmark_opts used to add these two flags, but had the same
descriptions for the flags regardless of what command took them and didn't
allow specifying flags more than once (no '*' at the start). Even more
importantly, it assumed that -B was always expecting an argument (i.e.
--bookmark=foo), but in case of incoming and outgoing it's not so (--bookmarks
is self-sufficient).
Differential Revision: https://phab.mercurial-scm.org/D4612
$ hg init repo
$ cd repo
$ touch foo
$ hg ci -Am 'add foo'
adding foo
$ hg up -C null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
this should be stored as a delta against rev 0
$ echo foo bar baz > foo
$ hg ci -Am 'add foo again'
adding foo
created new head
$ hg debugindex foo
rev linkrev nodeid p1 p2
0 0 b80de5d13875 000000000000 000000000000
1 1 0376abec49b8 000000000000 000000000000
$ cd ..