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luckydude | 1 year ago

My issues with Git

- No rename support, it guesses

- no weave. Without going into a lot of detail, suppose someone adds N bytes on a branch and then that branch is merged. The N bytes are copied into the merge node (yeah, I know, git looks for that and dedups it but that is a slow bandaid on the problem).

- annotations are wrong, if I added the N bytes on the branch and you merged it, it will (unless this is somehow fixed now) show you as the author of the N bytes in the merge node.

- only one graph for the whole repository. This causes multiple problems: A) the GCA is the repository GCA, it can be miles away from the file GCA if there was a graph per file like BitKeeper has. B) Debugging is upside down, you start at the changeset and drill down. In BitKeeper, because there is a graph per file, let's say I had an assert() pop. You run bk revtool on that file, find the assert and look around to see what has changed before that assert. Hover over a line, it will show you the commit comments to the file and then the changeset. You find the likely line, double click on it, now you are looking at the changeset. We were a tiny company, we never hit the claimed 25 people, and we supported tons of users. This form of debugging was a huge, HUGE, part of why we could support so many people. C) commit comments are per changeset, not per file. We had a graphic check in tool that walked you through the list of files, showed you the diffs for that file and asked you to comment. When you got the the ChangeSet file, now it is asking you for what Git asks for comments but the diffs are all the file names followed by what you just wrote. It made people sort of uplevel their commit comments. We had big customers that insisted the engineers use that tool rather a command line that checked in everything with the same comment.

- submodules turned Git into CVS. Maybe that's been redone but the last time I looked at it, you couldn't do sideways pulls if you had submodules. BK got this MUCH closer to correct, the repository produced identical results to a mono repository if all the modules were present (and identical less whatever isn't populated in the sparse case). All with exactly the same semantics, same functionality mono or many repos.

- Performance. Git gets really slow in large repositories, we put a ton of work into that in BitKeeper and we were orders of magnitude faster for things like annotate.

In summary, Git isn't really a version control system and Linus has admitted it to me years ago. A version control system needs to faithfully record everything that happened, no more or less. Git doesn't record renames, it passes content across branches by value, not by reference. To me, it feels like a giant step backwards.

Here's another thing. We made a bk fast-export and a bk fast-import that are compatible with Git. You can have a tree in BK, have it updated constantly, and no matter where in the history you run bk fast-export, you will get the same repository. Our fast-export is idempotent. Git can't do that, it doesn't send the rename info because it doesn't record that. That means we have to make it up when doing a bk fast-import which means Git -> BK is not idempotent.

I don't expect to convince anyone of anything at this point, someone nudged, I tried. I don't read hackernews any more so don't expect me to defend what I said, I really don't care at this point. I'm happier away from tech, I just go fish on the ocean and don't think about this stuff.

discuss

order

account42|1 year ago

> No rename support, it guesses

Git doesn't track changes yes, it tracks states. It has tools to compare those states but doesn't mean that it needs to track additional data to help those tools.

I'm unconvinced that tracking renames is really helpful as that is only the simplest case of of many possible state modifications. What if you split a file A into files B and C? You'd need to be able to track that too. Same for merging one file into another. And many many many more possible modifications. It makes sense to instead focus on the states and then improve the tools to compare them.

Tracking all kinds of changes also requires all development tools to be aware of your version control. You can no longer use standard tools to do mass renames and instead somehow build them on top of your vcs so it can track the operations. That's a huge tradeoff that tracking repository states doesn't have.

> submodules

I agree, neither submodules nor subtrees are ideal solutions.

samus|1 year ago

> What if you split a file A into files B and C? You'd need to be able to track that too. Same for merging one file into another. And many many many more possible modifications.

I suppose Bitkeeper can meaningfully deal with that since their data model drills down into the file contents.

gwd|1 year ago

> You run bk revtool on that file, find the assert and look around to see what has changed before that assert. Hover over a line, it will show you the commit comments to the file and then the changeset. You find the likely line, double click on it, now you are looking at the changeset.

I still have fond memories of the bk revool. I haven't found anything since that's been as intuitive and useful.

anitil|1 year ago

I hadn't heard of the per-file graph concept, and I can see how that would be really useful. But I have to agree that going for a fish sounds marvellous.

luckydude|1 year ago

I fished today, 3 halibut. Fish tacos for the win! If you cook halibut, be warned that you must take it off at 125 degrees, let it get above that and it turns to shoe leather.