Hi, On Mon, 5 Oct 2009, Junio C Hamano wrote: > Johannes Schindelin <Johannes.Schindelin@xxxxxx> writes: > > >> > + if (prepare_revision_walk(&rev)) > >> > + message = "(revision walker failed)"; > >> > >> If prepare_revision_walk() failed for whatever reason, can we trust > >> fast_forward/fast_backward at this point? > > > > No, but it is not used in that case, either, because message is not NULL > > anymore. > > It is used in that case a few lines below to decide if you add the third > dot. That's why I asked. Well, fair enough. The answer is: yes, we can still trust fast_forward/fast_backward, as there is no question that if the first merge base (which must be the only merge base by definition, in this case) is either "left" or "right", it is fast_forward or fast_backward, respectively. So: no worries. > > I have no idea why "submodule --summary" uses --first-parent, but > > personally, I would _hate_ it not to see the merged commits in the > > diff. > > > > For a summary, you might get away with seeing > > > > > Merge bla > > > Merge blub > > > Merge this > > > Merge that > > > > but in a diff that does not cut it at all. > > As long as bla/blub/this/that are descriptive enough, I do not see at all > why you think "summary" is Ok and "diff" is not. If your response were > "it is just a matter of taste; to some people (or project) --first-parent > is useful and for others it is not", I would understand it, and it would > make sense to use (or not use) --first-parent consistently between this > codepath and "submodule --summary", though. You may be used to git.git's quality of naming the branches you merge. Sadly, this is not the common case. > > In any case, just to safe-guard against sick minds, I can add a check that > > says that left, right, and all the merge bases _cannot_ have any flags > > set, otherwise we output "(you should visit a psychiatrist)" or some such. > > I wouldn't suggest adding such a kludge. Being insulting to the user when > we hit a corner case _we_ cannot handle does not help anybody, does it? Well, I was a little exasperated when I wrote that that you want to handle that case. But of course, I should heed Postel's law, and handle the case. Maybe say something like "(uses superproject's commits)". > I see two saner options. Doing this list walking in a subprocess so that > you wouldn't have to worry about object flags at all in this case would > certainly be easier; the other option obviously is to have a separate > object pool ala libgit2, but that would be a much larger change. The reason why I insist avoiding a subprocess is performance. The same reason holds for a separate object pool: it would just impede the speed, AFAICT. Besides, I vividly remember what happened to a patch I posted to be able to just clear the current object pool. And I cannot imagine a patch introducing a second pool to be any less complicated. If you really want the case I illustrated (that the submodule actually contains commits that already have been shown in the superproject) to be handled showing the correct submodule summary (and with --first-parent, I think you will agree that it is a summary, even if it is embedded in a diff), I could imagine calling a subprocess (for simplicity reasons) _iff_ left, right, or any of the merge bases has a flag set. But I really, really, really want to avoid a fork() in the common case. I do have some users on Windows, and I do have a few submodules in that project. Having too many fork() calls there would just give Git a bad reputation. And it has enough of that, it does not need more. Ciao, Dscho -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html