"J. Bruce Fields" <bfields@xxxxxxxxxxxx> writes: > On Tue, Jan 09, 2007 at 01:20:27PM -0800, Junio C Hamano wrote: >> Jeff King <peff@xxxxxxxx> writes: >> >> > For example, with what's in next now, I can do this: >> > >> > git checkout v1.4.0 >> > hack hack hack >> > git commit -m -a 'some changes which will never be seen again' >> > git checkout v1.2.0 >> > >> > I thought the _point_ of the safety valve was not to lose those changes. >> >> Fair enough. >> >> We could always do the check upon "git checkout" from a detached >> HEAD state, whether it takes you back on some existing branch or >> leaves your HEAD still detached. > > Stupid question: why can't checkout do something like this? > > if we're currently not on a branch, fail if .git/PREV > doesn't point to the same commit as .git/HEAD. > > if we're checking out a non-branch, store its SHA1 into > .git/PREV. I do not want to think about the consequences of adding more cruft under .git/ directory. For example, should PREV be noticed by fsck and prune? What should various forms of 'git-reset' do with it? How does it interact with 'git-bisect'? Being able to test merge or even make commits without being on a branch is vastly useful. It might or might not lead to anywhere even after you make a handful commits -- and I would imagine that it would be very handy to be able to be lazy and not having to decide if it is worth a new branch. But that may be just my imagination; I generally prefer any feature that allows me to defer decision over something that makes me decide early. If Carl wants to do a patch to teach 'git-commit' (and all other things that can create commits) not to do things from working in a detached HEAD, I would probably not opposed to it too much, but I am fairly certain that I won't be coding it myself. It's tempting to forget about this whole "safety" business. Because we allow "reset --hard" and other forms of operations that can lose history if they were done while on a branch, only giving the safety to "git checkout" feels somewhat silly. And the primary motive for detached HEAD as I understand it is for sightseeing, and not allowing "reset --hard" to jump around is just plain silly. That is, after: git checkout v1.4.0 you are not on any branch, and we would still allow git reset --hard v1.2.0 which is exactly the same as: git checkout v1.2.0 You can still say: git checkout master and we do not even check. Which makes the "merge-base --check-ancestry" stuff I did last night pretty much unnecessary, but that's Ok. It will find other uses. - 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