On Wed, 2016-03-09 at 15:41 +0100, Laszlo Ersek wrote: > According to your description, QEMU uses git improperly, so does > libvirt, and the KVM (kernel) queue too.
Let's see... Imagine I'm working on a new feature, and I submit a carefully tested sequence of commits in a pull request. Someone *rebases* my work onto a different point in history, which introduces a bug. The record now shows that I submitted something *broken*. Like https://github.com/openssl/openssl/commit/963bb621 for example, which is utterly hosed and broke the build for everyone except me. On that occasion, I was able to look back at what I *actually* submitted and point out that it wasn't my fault. But sometimes the breakage is more subtle. You end up looking back a few months later and trying to work out why an esoteric corner case is failing. You might ask me, and I'll say that I *distinctly* remember I thought about it, and that I could have sworn I *had* tested it.... But again the record shows that what got merged has *never* worked. That's no longer just a problem of embarrassment for the submitter, by misrepresenting their work. That's now causing problems for the *project*. Because if history had been represented *correctly*, with a working commit and then a subsequent merge introducing the breakage, then that is a *whole* lot easier to figure out. Preserving accurate history is a large part of the reason we *have* version control systems. And yes, if any of those projects you list are deliberately throwing away history as a matter of course on non-trivial submissions, then I would say that they are using the tools improperly. Of course, for simple patches it often makes no difference (well, apart from the OpenSSL example I gave above). And for larger submissions it doesn't *often* make a difference. But that's not the point. Sure, let people apply their *discretion* about rebasing stuff, if you really must — but a workflow which *enforces* a rebase, and *never* lets you pull a complex submission as it *actually* happened, is quite wrong. -- dwmw2
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