Failed qimport of patches from files should cleanup by recording successfully
imported patches in series file.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init repo
$ cd repo
$ echo a > a
$ hg ci -Am'add a'
adding a
$ cat >b.patch<<EOF
> diff --git a/a b/a
> --- a/a
> +++ b/a
> @@ -1,1 +1,2 @@
> a
> +b
> EOF
$ echo
empty series
$ hg qseries
$ echo
qimport valid patch followed by invalid patch
$ hg qimport b.patch fakepatch
adding b.patch to series file
abort: unable to read file fakepatch
[255]
$ echo
valid patches before fail added to series
$ hg qseries
b.patch