Hi, Christian and Ævar First of all, thanks for the fast and attentive reviews. I am a little confused about what I should do next. How should I proceed with this series? By what was said, I understood that the series: 1) Is indeed an improvement under --local, because it won't deference symlinks in this case. 2) Don't make --dissociate any better but as it is already buggy that would be some work for another patchset. 3) Makes git-clone copy hidden paths which is a good behaviour. 4) Breaks --no-hardlinks when there are symlinks at the repo's objects directory. I understood that even though git itself does not create symlinks in .git/objects, we should take care of the case where the user manually creates them, right? But what would be the appropriate behaviour: to follow (i.e. deference) symlinks (the way it is done now) or just copy the link file itself (the way my series currently do)? And shouldn't we document this decision somewhere? About the failure with --no-hardlinks having symlinks at .dir/objects, it's probably because copy_or_link_directory() is trying to copy a file which is a symlink to a dir and the copy function used is trying to copy the dir not the link itself. A possible fix is to change copy.c to copy the link file, but I haven't studied yet how that could be accomplished. Another possible fix is to make copy_or_link_directory() deference symlink structures when --no-hardlinks is given. But because the function falls back to no-hardlinks when failing to hardlink, I don't think it would be easy to accomplish this without making the function *always* deference symlinks. And that would make the series lose the item 1), which I understand you liked. So, what would be the best here? Best, Matheus Tavares On Sun, Feb 24, 2019 at 6:41 AM Christian Couder <christian.couder@xxxxxxxxx> wrote: > > On Sat, Feb 23, 2019 at 11:48 PM Ævar Arnfjörð Bjarmason > <avarab@xxxxxxxxx> wrote: > > > > > > On Sat, Feb 23 2019, Matheus Tavares wrote: > > > > > Replace usage of opendir/readdir/closedir API to traverse directories > > > recursively, at copy_or_link_directory function, by the dir-iterator > > > API. This simplifies the code and avoid recursive calls to > > > copy_or_link_directory. > > > > Sounds good in principle. > > > > > This process also brings some safe behaviour changes to > > > copy_or_link_directory: > > > > I ad-hoc tested some of these, and could spot behavior changes. We > > should have tests for these. > > I agree that ideally we should have a few tests for these, but this is > a grey area (see below) and there are areas that are not grey for > which we don't have any test... > > And then adding tests would make this series become larger than a > typical GSoC micro-project... > > > > - It will no longer follows symbolic links. This is not a problem, > > > since the function is only used to copy .git/objects directory, and > > > symbolic links are not expected there. > > > > I don't think we should make that assumption, and I don't know of > > anything else in git that does. > > I think Git itself doesn't create symlinks in ".git/objects/" and we > don't recommend people manually tweaking what's inside ".git/". That's > why I think it's a grey area. > > > I've certainly symlinked individual objects or packs into a repo for > > debugging / recovery, and it would be unexpected to clone that and miss > > something. > > If people tweak what's inside ".git" by hand, they are expected to > know what they doing and be able to debug it. > > > So in the general case we should be strict in what we generate, but > > permissive in what we accept. We don't want a "clone" of an existing > > repo to fail, or "fsck" to fail after clone... > > Yeah, but realistically I don't think we are going to foolproof Git > from everything that someone could do by tweaking random things > manually in ".git/". > > I am not saying that it should be ok to make things much worse than > they are now in case some things have been tweaked in ".git/", but if > things in general don't look worse in this grey area, and a patch > otherwise improves things, then I think the patch should be ok. > > > When trying to test this I made e.g. objects/c4 a symlink to /tmp/c4, > > and a specific object in objects/4d/ a symlink to /tmp too. > > > > Without this patch the individual object is still a symlink, but the > > object under the directory gets resolved, and "un-symlinked", also with > > --dissociate, which seems like an existing bug. > > > > With your patch that symlink structure is copied as-is. That's more > > faithful under --local, but a regression for --dissociate (which didn't > > work fully to begin with...). > > I think that I use --local (which is the default if the repository is > specified as a local path) much more often than --dissociate, so for > me the patch would be very positive, especially since --dissociate is > already buggy anyway in this case. > > > I was paranoid that "no longer follows symbolic links" could also mean > > "will ignore those objects", but it seems to more faithfully copy things > > as-is for *that* case. > > Nice! > > > But then I try with --no-hardlinks and stock git dereferences my symlink > > structure, but with your patches fails completely: > > > > Cloning into bare repository 'repo2'... > > error: copy-fd: read returned: Is a directory > > fatal: failed to copy file to 'repo2/objects/c4': Is a directory > > fatal: the remote end hung up unexpectedly > > fatal: cannot change to 'repo2': No such file or directory > > Maybe this could be fixed. Anyway I don't use --no-hardlinks very > often, so I still think the patch is a positive even with this > failure. > > > So there's at least one case in a few minutes of prodding this where we > > can't clone a working repo now, however obscure the setup. > > > > > - Hidden directories won't be skipped anymore. In fact, it is odd that > > > the function currently skip hidden directories but not hidden files. > > > The reason for that could be unintentional: probably the intention > > > was to skip '.' and '..' only, but it ended up accidentally skipping > > > all directories starting with '.'. Again, it must not be a problem > > > not to skip hidden dirs since hidden dirs/files are not expected at > > > .git/objects. > > > > I reproduce this with --local. A ".foo" isn't copied before, now it > > is. Good, I guess. We'd have already copied a "foo". > > > > > - Now, copy_or_link_directory will call die() in case of an error on > > > openddir, readdir or lstat, inside dir_iterator_advance. That means > > > it will abort in case of an error trying to fetch any iteration > > > entry. > > It would be nice if the above paragraph in the commit message would > say what was the previous behavior and why it's better to die() . > > > Good, but really IMNSHO this series is tweaking some critical core code > > and desperately needs tests. > > It's critical that this code works well in the usual case, yes. (And > there are already a lot of tests that test that.) But when people have > manually tweaked things in their ".git/objects/", it's not critical > what happens. Many systems have "undefined behaviors" at some point > and that's ok. > > And no, I am not saying that we should consider it completely > "undefined behavior" as soon as something is manually tweaked in > ".git/", and yes, tests would be nice, and your comments and manual > tests on this are very much appreciated. It's just that I don't think > we should require too much when a patch, especially from a first time > contributor, is already improving things, though it also changes a few > things in a grey area. > > > Unfortunately, in this as in so many edge case we have no existing > > tests. > > > > This would be much easier to review and would give reviewers more > > confidence if the parts of this that changed behavior started with a > > patch or patches that just manually objects/ dirs with various > > I think "created" is missing between "manually" and "objects/" in the > above sentence. > > > combinations of symlinks, hardlinks etc., and asserted that the various > > options did exactly what they're doing now, and made sure the > > source/target repos were the same after/both passed "fsck". > > > > Then followed by some version of this patch which changes the behavior, > > and would be forced to tweak those tests. To make it clear e.g. that > > some cases where we have a working "clone" are now a hard error. > > Unfortunately this would be a lot of work and not appropriate for a > GSoC micro-project. > > Thanks, > Christian.
