backout: use "getcommiteditor()" instead of explicit editor choice This patch also enhances "test-backout.t", because "hg backout" hasn't been explicitly tested around editor invocation and '--edit' option.

backout: avoid redundant message examination Before this patch, "hg backout" examines "--message" and "--logfile" options explicitly. But this examination is redundant, because "commitfunc()" can receive the result of same examination by "cmdutil.logmessage()" in "cmdutil.commit()" through "message" argument. This patch avoids redundant message examination by "message" examination in "commitfunc()".

transplant: use "getcommiteditor()" instead of explicit editor choice This patch also enhances "test-transplant.t", because "hg transplant" hasn't been explicitly tested around editor invocation and "--edit" option.