histedit: record histedit source (issue3681) Have histedit record the hex of the original changeset as already done by: - graft - commit --amend - rebase My main motivation for adding this is to prevent the creation of obsolescence cycle (see issue3681). Note that commit created during edit are not affected yet.

histedit: factor most commit creation in a function Later commits add two important items to histedit: - Obsolescence cycle prevention - Proper phase conservation Those logics must be applied to all simple operations (pick, edit, mess) and will require verbose code. So we introduce a new function that will provide an entry point for this new. logic. The function build a closure to have a clear distinction between commit arguments and data provided to the function to fulfil its logic.