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Subversion considered obsoleteSubversion considered obsoletePosted Apr 6, 2010 19:03 UTC (Tue) by vonbrand (subscriber, #4458)In reply to: Subversion considered obsolete by Msemack Parent article: A proposed Subversion vision and roadmap
Locking is not needed in git, all changes are atomic by design. Sure, if several people mess around commiting stuff at random into the same repo, caos could ensue (but "lock for a commit" won't help here anyway). A solution is to have a real person as a gatekeeper for changes. Or use something like gitolite to provide finer-grained access to a shared repo.
"Large files can't be handled"? That I don't see where it comes from. Sure, early
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Subversion considered obsolete Posted Apr 6, 2010 23:16 UTC (Tue) by dlang (✭ supporter ✭, #313) [Link]
git currently requires that any file it manipulates get mmapped, this limits the file size to your memory size.
git's pack file format uses 32 bit offsets, which limits the largest pack size to ~4G (I believe it uses unsigned 32 bit values, if it's signed values then the limit is 2G) I think that it is always pointing to the beginning of a file, so a file larger than 4G can exist in a pack, but would be the only thing in the pack.
Size limit in git objects? Posted Apr 7, 2010 1:02 UTC (Wed) by vonbrand (subscriber, #4458) [Link]
Wrong. From Observation: length of each object is encoded in a variable length format and is not constrained to 32-bit or anything.
Size limit in git objects? Posted Apr 7, 2010 3:23 UTC (Wed) by dlang (✭ supporter ✭, #313) [Link]
the length of the object isn't contrained, but the offset to the start of the object is.
so you can have up to 4G in a pack file, plus however much the last object runs off the end of it.
Subversion considered obsolete Posted Apr 7, 2010 22:56 UTC (Wed) by cmccabe (guest, #60281) [Link]
> git currently requires that any file it manipulates get mmapped, this
> limits the file size to your memory size.
You can mmap(2) files that are bigger than your memory size.
Of course, if you're on 32-bit, there are some size limitations because of the limited size of virtual memory.
Subversion considered obsolete Posted Apr 7, 2010 20:21 UTC (Wed) by tialaramex (subscriber, #21167) [Link]
The locking people are talking about isn't locking for a commit
What happens in many proprietary systems, and in subversion if you choose, is that you need a lock to be "authorised" to edit a file, not to commit the change. The procedure looks like:
1 The lockable files start off read-only
The VCS can't strictly _enforce_ the locking rule, of course you could copy file X, or set it read-write manually, then start working on it, and only try to take the lock a day later. But, when you complain to your boss that someone changed file X after you'd started work on it, of course he won't have much sympathy.
The locking model has lots of problems, but some people have convincing arguments for why its appropriate to their problem. The only options for Git are (1) not appealing to those users (2) persuading them all that they're wrong or (3) offering some weird hybrid mode where there can be a central locking server for a subset of files. If you accept that (1) could be the right option, then the continued existence of Subversion is justified for those users already.
Subversion considered obsolete Posted Apr 8, 2010 20:56 UTC (Thu) by vonbrand (subscriber, #4458) [Link] In centralized systems (especially those that don't handle merges decently) this is really the only way to work, true. (RCS works this way, for example). But with decentralized systems with reasonable branching and merging this isn't required. And locking a file doesn't really make sense in a decentralized system (there is no single "file" to lock!), so it is left out of the tool. If the workflow requires some sort of "don't touch some file(s) for a while" synchronization, it has to be handled outside. I believe this requirement's importance is way overblown. How many projects do you work on, where it is really a requirement (not an artifact of shortcommings in integrating changes by the tool)?
Subversion considered obsolete Posted Apr 8, 2010 21:56 UTC (Thu) by foom (subscriber, #14868) [Link]
Subversion's locking is purely a workflow management tool: it *is* simply a way to say "don't touch this file for a while".
Being a distributed VCS doesn't make this workflow management tool any less necessary. And it's convenient to have it integrated with the VCS so that "status" shows the status, and "commit" checks and releases the locks, and so on.
You might want to read this so you can know what you're talking about:
I wish I didn't have to keep defending subversion: git is really nice. But come on people, just be honest about what it can't do, and stop claiming those things are unnecessary!
Subversion considered obsolete Posted Apr 9, 2010 16:07 UTC (Fri) by vonbrand (subscriber, #4458) [Link] As I said, the workflow might require it. But in a decentralized environment there simply can't be any "common rallying point" for all developers handled by the DVCS, so the tool itself can't help you here. Not by a design flaw, but by fundamental reasons: The "locking" idea only makes sense if there is one master copy shared by all.
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