[PATCH 0 of 1 V2] histedit: abort if there are multiple roots in "--outgoing" revisions

[FUJIWARA Katsunori]

This patch series makes "histedit --outgoing" aborts if there are
multiple roots in "--outgoing" revisions.

With patch in V1 series, "histedit --outgoing" was equivalent to
"histedit 'outgoing() and ::.'".