On Tue, Jan 16 2024, Karthik Nayak wrote: > Pratyush Yadav <me@xxxxxxxxxxxxxxxxx> writes: > >> Hi, >> > > Hello, > >> I ran into a strange Magit bug, where when I ran magit-show-refs on a >> particular repo it threw an error. The details of the Magit bug are not >> very interesting, but when attempting to reproduce it, I also saw git >> misbehaving for such repos. >> >> The strange behaviour happens when you push a commit object to remote's >> refs/HEAD instead of pushing a symbolic ref. Such a repository can be >> found at https://github.com/prati0100/magit-reproducer. I roughly used >> the below steps to create such a repo: >> >> $ git init >> $ echo 1 > foo && git add foo && git commit >> $ echo 2 > bar && git add bar && git commit >> $ git push >> $ git checkout 79264c3 >> $ echo 2.1 > bar && git add bar && git commit >> $ git push origin 707a3d5:refs/heads/HEAD >> > > Just to note here that pushing to "refs/heads/HEAD" is not actually > updating the remote repositories $GIT_DIR/HEAD file, rather it creates a > new reference $GIT_DIR/refs/heads/HEAD. Yes, that is what I would also expect. I checked one of the Git servers we have and this is exactly what happens. $GIT_DIR/HEAD is a symref pointing to refs/heads/main and $GIT_DIR/refs/heads/HEAD points to the commit. But behaviour from client side is not consistent. > > With this understanding you'll see that this is not a bug, because the > remote HEAD was never updated, but only a new branch called HEAD was > created [0]. GitHub thinks so but try opening the branch. It won't show you the commit (707a3d5, "2.1") but instead shows you 86e1c97 ("2"). So something is wrong _at least_ with Github. > >> Now with such a repo, if you do `git log --all --oneline` it would look >> something like: >> >> 707a3d5 (origin/HEAD) 2.1 >> 86e1c97 (HEAD -> main, origin/main) 2 >> 79264c3 1 >> >> And running `git for-each-ref --format='%(symref:short),%(refname:short),%(refname),%(subject)' refs/remotes/origin` gives: >> >> ,origin,refs/remotes/origin/HEAD,2.1 >> ,origin/main,refs/remotes/origin/main,2 >> >> All well and good so far. Now delete the repo and attempt to clone it. >> This time `git log --all --oneline` gives: >> >> 86e1c97 (HEAD -> main, origin/main, origin/HEAD) 2 >> 79264c3 1 >> > > This is expected since you cloned the repository and you got the default > branch 'main'. No. First, if I clone a repo with multiple branches (say https://github.com/prati0100/git-gui) I get _all_ the remote branches. Yet here I clearly don't get the so called "HEAD" branch. This is not expected behaviour. Second, git really does misunderstand refs/remotes/origin/HEAD. For example, when running git for-each-ref command with the clone method, I get: origin/main,origin,refs/remotes/origin/HEAD,2 So it clearly thinks refs/remotes/origin/HEAD is at 86e1c97 ("2"). Or, to be more specific, it thinks the ref points to origin/main which is at 86e1c97 ("2"). But we set it at (707a3d5, "2.1"). So it tells me the wrong thing. Now if I do the git remote add && git remote update method, git for-each-ref says: ,origin,refs/remotes/origin/HEAD,2.1 So now it thinks refs/remotes/origin/HEAD points at (707a3d5, "2.1"). I do not see it as expected behaviour. We can also see this when inspecting the contents of .git/refs/remotes/origin/HEAD. With clone it says: ref: refs/remotes/origin/main With git remote add && git remote update it says: 707a3d587c61c089710e3924eb63a51763b5a4c8 The same ref points to different places based on how you pull the repo. Looking deeper, if you clone a repo that does not have a branch called "HEAD" (like git-gui), git creates a file in .git/refs/remotes/origin/HEAD that says: ref: refs/remotes/origin/master So it certainly seems to use refs/remotes/origin/HEAD to point to the remote's HEAD, and not as a regular branch. I find this to be inconsistent behaviour on git's part and do not think it is (or should be) expected behaviour. > >> And running `git for-each-ref --format='%(symref:short),%(refname:short),%(refname),%(subject)' refs/remotes/origin` gives: >> >> origin/main,origin,refs/remotes/origin/HEAD,2 >> ,origin/main,refs/remotes/origin/main,2 >> >> So suddenly the remote's HEAD becomes origin/main (symbolic ref) and the >> commit (707a3d5, "2.1") is nowhere to be found. It neither shows up in >> `git rev-list --all` nor in `git log --all`. The files and trees >> associated with it also do not show up in `git rev-list --all --object`. > > > Because rev-list's `--all`, iterates over all refs. Since you only > cloned, the HEAD branch is not pulled. Why not? When you clone all branches should get pulled. > > Everything else is a consequence of the subtle but important difference > between updating $GIT_DIR/HEAD vs creating $GIT_DIR/refs/heads/HEAD. > > [0]: https://github.com/prati0100/magit-reproducer/branches/all -- Regards, Pratyush Yadav
