builddependencies: don't add dependency on revision outside input set
This was already handled in the single-successor case, but had been
missed in the multiple-successors case.
Note that there seems to be a copy of builddependencies() in the
topics extension. I don't use topics more than I have to, so I'll let
someone else fix that code.
testing topic with shelve extension
------------------------------------
$ . "$TESTDIR/testlib/topic_setup.sh"
$ hg init repo
$ cd repo
$ cat <<EOF >>.hg/hgrc
> [extensions]
> shelve=
> EOF
$ touch a
$ echo "Hello" >> a
$ hg topic "testing-shelve"
marked working directory as topic: testing-shelve
$ hg topic
* testing-shelve (0 changesets)
$ hg ci -m "First commit" -A
adding a
active topic 'testing-shelve' grew its first changeset
$ hg topic
* testing-shelve (1 changesets)
$ echo " World" >> a
$ hg stack
### topic: testing-shelve
### target: default (branch)
t1@ First commit (current)
shelve test
-----------
$ hg shelve
shelved as default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg topic
* testing-shelve (1 changesets)
$ hg stack
### topic: testing-shelve
### target: default (branch)
t1@ First commit (current)
unshelve test
-------------
$ hg unshelve
unshelving change 'default'
$ hg topic
* testing-shelve (1 changesets)
$ hg stack
### topic: testing-shelve
### target: default (branch)
t1@ First commit (current)