Question about commit message conventions

Hi,

although I've read the documentation of git very carefully, I could not find anything related to certain commit message conventions. It would be great if someone here could explain a few things, maybe this could be added to the wiki afterwards (<http://git.or.cz/gitwiki/CommitMessageConventions>).

First of all, what's the intended use of the "Signed-off-by:" lines? Does it make sense to add my name there, even when I'm listed as the author or committer of a commit? I thought that they are intended mostly to note the approval of other developers.

On the other hand, concerning the approval of other developers, what's the difference between "Signed-off-by:" and "Acked-by:"? Are there any more "*-by:" fields that are in use?

Regards, Tobias