[PATCH 0 of 3] graft, rebase, transplant: Set HGREVISION variable for an editor

[Alexander Drozdov]

The patch series makes Mercurial to set HGREVISION environment variable for
an editor on graft, rebase or transplant commands.

Also, please see related discussion:
http://selenic.com/pipermail/mercurial/2011-November/040641.html