histedit: use str.startswith to check for comments in action list

histedit: drop duplicate line extracting keep option

import: avoid editor invocation when importing with "--exact" for exact-ness Before this patch, external editor is invoked when imported patch has no commit message, even if "--exact" is specified. Then, exact-ness is broken, because empty commit message causes failure of committing. This patch avoids editor invocation at importing with "--exact" for exact-ness, because commit message in the patch should be kept as it is in such case, even if it is empty.

import: disallow meaningless combination of "--exact" and "--edit" Before this patch, "hg import" allows combination of "--exact" and "--edit", even though editing commit message breaks exact-ness. This patch disallows meaningless combination of "--exact" and "--edit".