[PATCH 0 of 4] graft, rebase, transplant: Set HGREVISION variable for an editor V2

[Alexander Drozdov]

The patchset makes Mercurial to set HGREVISION environment variable for
an editor on graft, rebase and transplant commands.

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