exchange: create transaction for bundle1 unbundling earlier
changegroup.apply() currently creates a transation if there isn't
already one. Having the callers of that method pass in an existing
transaction seems a little cleaner. To do that, we need to make sure
all callers have a transaction. Since the transaction name is used as
a hook argument (HG_TXNNAME), we need to match the name from
changegroup.apply().
#require symlink
https://bz.mercurial-scm.org/1438
$ hg init
$ ln -s foo link
$ hg add link
$ hg ci -mbad link
$ hg rm link
$ hg ci -mok
$ hg diff -g -r 0:1 > bad.patch
$ hg up 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg import --no-commit bad.patch
applying bad.patch
$ hg status
R link
? bad.patch