templatekw: inline showlist() into showbookmarks()
showlist() is the helper to build _hybrid object from a trivial list. It can't
be applied if each value has more than one items, 'bookmark' and 'current' in
this case.
This change is necessary to fix random failure of "{join(bookmarks, sep)}".
Test issue2761
$ hg init
$ touch to-be-deleted
$ hg add
adding to-be-deleted
$ hg ci -m first
$ echo a > to-be-deleted
$ hg ci -m second
$ rm to-be-deleted
$ hg diff -r 0
Same issue, different code path
$ hg up -C
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ touch does-not-exist-in-1
$ hg add
adding does-not-exist-in-1
$ hg ci -m third
$ rm does-not-exist-in-1
$ hg diff -r 1