So I'm in the process of getting GIT sold at work. First thing I need is to convince everyone that GIT is better at what they're already used to doing. We currently use Perforce. Anybody else go through a similar sale? Any good links/advice?
One of the big wins is that we can work with it disconnected from the network. Another win IMO is the way adds/checkouts are handled. More points are welcome! Also we have about 10-20 devs total.
I use Perforce at work. I also use Git because I would still like some form of version control when I'm working on code and can't connect to the server. No, reconcile offline work just is not the same. Here is where I've found git to be a great benefit:
Well, that's my 2 cents. In Perforce's defense, I gotta say their customer support rules and so does their Time Lapse View tool. I do not know how to get a time lapse view with git. But for the convenience and time saved, I'd go with git any day.
The Perl 5 interpreter source code is currently going through the throes of converting from Perforce to git. Maybe Sam Vilain’s git-p4raw importer is of interest.
In any case, one of the major wins you’re going to have over every centralised VCS and most distributed ones also is raw, blistering speed. You can’t imagine how liberating it is to have the entire project history at hand, mere fractions of fractions of a second away, until you have experienced it. Even generating a commit log of the whole project history that includes a full diff for each commit can be measured in fractions of a second. Git is so fast your hat will fly off. VCSs that have to roundtrip over the network simply have no chance of competing, not even over a Gigabit Ethernet link.
Also, git makes it very easy to be carefully selective when making commits, thereby allowing changes in your working copy (or even within a single file) to be spread out over multiple commits – and across different branches if you need that. This allows you to make fewer mental notes while working – you don’t need to plan out your work so carefully, deciding up front what set of changes you’ll commit and making sure to postpone anything else. You can just make any changes you want as they occur to you, and still untangle them – nearly always quite easily – when it’s time to commit. The stash can be a very big help here.
I have found that together, these facts cause me to naturally make many more and much more focused commits than before I used git. This in turn not only makes your history generally more useful, but is particularly beneficial for value-add tools such as git bisect.
I’m sure there are more things I can’t think of right now. One problem with the proposition of selling your team on git is that many benefits are interrelated and play off each other, as I hinted at above, such that it is hard to simply look at a list of features and benefits of git and infer how they are going to change your workflow, and which changes are going to be bonafide improvements. You need to take this into account, and you also need to explicitly point it out.
It would take me a lot of convincing to switch from perforce. In the two companies I used it it was more than adequate. Those were both companies with disparate offices, but the offices were set up with plenty of infrastructure so there was no need to have the disjoint/disconnected features.
How many developers are you talking about changing over?
The real question is - what is it about perforce that is not meeting your organization's needs that git can provide? And similarly, what weaknesses does git have compared to perforce? If you can't answer that yourself then asking here won't help. You need to find a business case for your company. (e.g. Perhaps it is with lower overall cost of ownership (that includes loss of productivity for the interim learning stage, higher admin costs (at least initially), etc.)
I think you are in for a tough sell - perforce is a pretty good one to try to replace. It is a no brainer if you are trying to boot out pvcs or ssafe.
I think in terms of keeping people happy during/ post switch over, one of things to get across early is just how private a local branch can be in Git, and how much freedom that gives them to make mistakes. Get them all to clone themselves a few private branches from the current code and then go wild in there, experimenting. Rename some files, check stuff in, merge things from another branch, rewind history, rebase one set of changes on top of another, and so on. Show how even their worst accidents locally have no consequences for their colleagues. What you want is a situation where developers feel safe, so they can learn faster (since Git has a steep learning curve that's important) and then eventually so that they're more effective as developers.
When you're trying to learn a centralised tool, obviously you will be worried about making some goof that causes problems for other users of the repository. The fear of embarrassment alone is enough to discourage people from experimenting. Even having a special "training" repository doesn't help, because inevitably developers will encounter a situation in the production system that they never saw during training, and so they're back to worrying.
But Git's distributed nature does away with this. You can try any experiment in a local branch, and if it goes horribly wrong, just throw the branch away and nobody needs to know. Since you can create a local branch of anything, you can replicate a problem you're seeing with the real live repository, yet have no danger of "breaking the build" or otherwise making a fool of yourself. You can check absolutely everything in, as soon as you've done it, no trying to batch work up into neat little packages. So not just the two major code changes you spent four hours on today, but also that build fix that you remembered half way through, and the spelling mistake in the documentation you spotted while explaining something to a colleague, and so on. And if the major changes are abandoned because the project is changing direction, you can cherry pick the build fix and the spelling mistake out of your branch and keep those with no hassle.
The command that sold me on git personally was bisect. I don't think that this feature is available in any other version control system as of now.
That being said, if people are used to a GUI client for source control they are not going to be impressed with git. Right now the only full-featured client is command-line.
What Perforce features are people using?
I ask because if all folks are doing is get and put from the command line, git has that covered, and so do all the other RTS.
Apparently GitHub now offer git training courses to companies. Quoth their blog post about it:
I’ve been down to the Google campus a number of times in the last few weeks helping to train the Androids there in Git. I was asked by Shawn Pearce (you may know him from his Git and EGit/JGit glory – he is the hero that takes over maintanance when Junio is out of town) to come in to help him train the Google engineers working on Andriod in transitioning from Perforce to Git, so Android could be shared with the masses. I can tell you I was more than happy to do it.
[…]
Logical Awesome is now officially offering this type of custom training service to all companies, where we can help your organization with training and planning if you are thinking about switching to Git as well.
Emphasis mine.
I have been using Perforce for a long time and recently I also started to use GIT. Here is my "objective" opinion:
Perforce features:
GIT features:
Overall for OpenSource/Distributed projects I would always recommend GIT, because it is more like a P2P application and everyone can participate in development. For example, I remember that when I was doing remote development with Perforce I was syncing 4GB Projects over 1Mbps link once in a week. Alot of time was simply wasted because of that. Also we needed set up VPN to do that.
If you have a small company and P4 server will be always up then I would say that Perforce is also a very good option.
We have been using Git for sometime, recently our Git server's harddrive crashed and we could not revert back to the latest state. We managed to get back to few days old state. When the server was back up. Everyone in the team pulled/pushed their changes and voila, the server is back to current state.
I think the one thing that I know GIT wins on is it's ability to "preserve line endings" on all files, whereas perforce seems to insist on translating them into either Unix, Dos/Windows or MacOS9 format ("\n", "\r\n" or "\r).
This is a real pain if you're writing Unix scripts in a Windows environment, or a mixed OS environment. It's not even possible to set the rule on a per-file-extension basis. For instance, it would convert .sh, .bash, .unix files to Unix format, and convert .ccp, .bat or .com files to Dos/Windows format.
In GIT (I'm not sure if that's default, an option or the only option) you can set it up to "preserve line endings". That means, you can manually change the line endings of a file, and then GIT will leave that format the way it is. This seems to me like the ideal way to do things, and I don't understand why this isn't an option with Perforce.
The only way you can achieve this behavior, is to mark the files as binary. As I see that, that would be a nasty hack to workaround a missing feature. Apart from being tedious to have to do on all scripts, etc, it would also probably break most diffs, etc.
The "solution" that we've settled for at the moment, is to run a sed command to remove all carriage returns from the scripts every time they're deployed to their Unix environment. This isn't ideal either, especially since some of them are deployed inside WAR files, and the sed line has to be run again when they're unpacked.
This is just something I think gives GIT a great advantage, and which I don't think has been mentioned above.
EDIT: After having been using Perforce for a bit longer, I'd like to add another couple of comments:
A) Something I really miss in Perforce is a clear and instance diff, including changed, removed and added files. This is available in GIT with the git diff command, but in Perforce, files have to be checked out before their changes are recorded, and while you might have your main editors (like Eclipse) set up to automatically check files out when you edit them, you might sometimes edit files in other ways (notepad, unix commands, etc). And new files don't seem to be added automatically at all, even using Eclipse and p4eclipse, which can be rather annoying. So to find all changes, you have to run a "Diff against..." on the entire workspace, which first of all takes a while to run, and secondly includes all kind of irrelevant things unless you set up very complicated exclusion lists, which leads me to the next point.
B) In GIT I find the .gitignore very simple and easy to manage, read and understand. However, the workspace ignore/exclude lists configurable in Perforce seem unwieldy and unnecessarily complex. I haven't been able to get any exclusions with wildcards working. I would like to do something like
-//Server/mainline/.../target/... //Svend_Hansen_Server/.../target/...
To exclude all target folders within all projects inside Server/mainline. However, this doesn't seem to work like I would have expected, and I've ended up adding a line for every project like:
-//Server/mainline/projectA/target/... //Svend_Hansen_Server/projectA/target/...
-//Server/mainline/projectB/target/... //Svend_Hansen_Server/projectB/target/...
...
And similar lines for bin folders, .classpath and .projet files and more.
C) In Perforce there are the rather useful changelists. However, assume I make a group of changes, check them all and put them in a changelist, to then work on something else before submitting that changelist. If I later make a change to one of the files included in the first changelist, that file will still be in that changelist, and I can't just later submit the changelist assuming that it only contains the changes that I originally added (though it will be the same files). In GIT, if you add a file and them make further changes to it, those changes will not have been added (and would still show in a git diff and you wouldn't be able to commit the file without first adding the new changes as well. Of course, this isn't usefull in the same way the changelist can be as you only have one set of added files, but in GIT you can just commit the changes, as that doesn't actually push them. You could them work on other changes before pushing them, but you wouldn't be able to push anything else that you add later, without pushing the former changes as well.
The one important difference between Perforce and git (and the one most commonly mentioned) is their respective handling of huge binary files.
Like, for example, in this blog of an employee at a video game development company: http://corearchitecture.blogspot.com/2011/09/git-vs-perforce-from-game-development.html
However, the important thing is that, the speed difference between git and perforce, when you have a huge 6gb repository, containing everything from documentation to every binary ever built (and finally, oh yes! the actual source history), usually comes from the fact that huge companies tend to run Perforce, and so they set it up to offload all significant operations to the huge server bank in the basement.
This important advantage on Perforce's part comes only from a factor that has nothing whatsoever to do with Perforce, the fact that the company running it can afford said server bank.
And, anyway, in the end, Perforce and git are different products. Git was designed to be solely a VCS, and it does this far better than Perforce (in that it has more features, which are generally easier to use, in particular, in the words of another, branching in Perforce is like performing open-heart surgery, it should only be done by experts :P ) ( http://stevehanov.ca/blog/index.php?id=50 )
Any other benefits which companies that use Perforce gain have come merely because Perforce is not solely a VCS, it's also a fileserver, as well as having a host of other features for testing the performance of builds, etc.
Finally: Git being open-source and far more flexible to boot, it would not be so hard to patch git to offload important operations to a central server, running mounds of expensive hardware.
I have no experience with Git, but I have with Mercurial which is also a distributed VCS. It depends on the project really, but in our case a distributed VCS suited the project as basically eliminated frequent broken builds.
I think it depends on the project really, as some are better suited towards a client-server VCS, and others towads a distributed one.
Here's what I don't like about git:
First of all, I think the distributed idea flies in the face of reality. Everybody who's actually using git is doing so in a centralised way, even Linus Torvalds. If the kernel was managed in a distributed way, that would mean I couldn't actually download the "official" kernel sources - there wouldn't be one - I'd have to decide whether I want Linus' version, or Joe's version, or Bill's version. That would obviously be ridiculous, and that's why there is an official definition which Linus controls using a centralised workflow.
If you accept that you want a centralised definition of your stuff, then it becomes clear that the server and client roles are completely different, so the dogma that the client and server softwares should be the same becomes purely limiting. The dogma that the client and server data should be the same becomes patently ridiculous, especially in a codebase that's got fifteen years of history that nobody cares about but everybody would have to clone.
What we actually want to do with all that old stuff is bung it in a cupboard and forget that it's there, just like any normal VCS does. The fact that git hauls it all back and forth over the network every day is very dangerous, because it nags you to prune it. That pruning involves a lot of tedious decisions and it can go wrong. So people will probably keep a whole series of snapshot repos from various points in history, but wasn't that what source control was for in the first place? This problem didn't exist until somebody invented the distributed model.
Git actively encourages people to rewrite history, and the above is probably one reason for that. Every normal VCS makes rewriting history impossible for all but the admins, and makes sure the admins have no reason to consider it. Correct me if I'm wrong, but as far as I know, git provides no way to grant normal users write access but ban them from rewriting history. That means any developer with a grudge (or who was still struggling with the learning curve) could trash the whole codebase. How do we tighten that one? Well, either you make regular backups of the entire history, i.e. you keep history squared, or you ban write access to all except some poor sod who would receive all the diffs by email and merge them by hand.
Let's take an example of a well-funded, large project and see how git is working for them: Android. I once decided to have a play with the android system itself. I found out that I was supposed to use a bunch of scripts called repo to get at their git. Some of repo runs on the client and some on the server, but both, by their very existence, are illustrating the fact that git is incomplete in either capacity. What happened is that I was unable to pull the sources for about a week and then gave up altogether. I would have had to pull a truly vast amount of data from several different repositories, but the server was completely overloaded with people like me. Repo was timing out and was unable to resume from where it had timed out. If git is so distributable, you'd have thought that they'd have done some kind of peer-to-peer thing to relieve the load on that one server. Git is distributable, but it's not a server. Git+repo is a server, but repo is not distributable cos it's just an ad-hoc collection of hacks.
A similar illustration of git's inadequacy is gitolite (and its ancestor which apparently didn't work out so well.) Gitolite describes its job as easing the deployment of a git server. Again, the very existence of this thing proves that git is not a server, any more than it is a client. What's more, it never will be, because if it grew into either it would be betraying it's founding principles.
Even if you did believe in the distributed thing, git would still be a mess. What, for instance, is a branch? They say that you implicitly make a branch every time you clone a repository, but that can't be the same thing as a branch in a single repository. So that's at least two different things being referred to as branches. But then, you can also rewind in a repo and just start editing. Is that like the second type of branch, or something different again? Maybe it depends what type of repo you've got - oh yes - apparently the repo is not a very clear concept either. There are normal ones and bare ones. You can't push to a normal one because the bare part might get out of sync with its source tree. But you can't cvsimport to a bare one cos they didn't think of that. So you have to cvsimport to a normal one, clone that to a bare one which developers hit, and cvsexport that to a cvs working copy which still has to be checked into cvs. Who can be bothered? Where did all these complications come from? From the distributed idea itself. I ditched gitolite in the end because it was imposing even more of these restrictions on me.
Git says that branching should be light, but many companies already have a serious rogue branch problem so I'd have thought that branching should be a momentous decision with strict policing. This is where perforce really shines...
In perforce you rarely need branches because you can juggle changesets in a very agile way. For instance, the usual workflow is that you sync to the last known good version on mainline, then write your feature. Whenever you attempt to modify a file, the diff of that file gets added to your "default changeset". When you attempt to check in the changeset, it automatically tries to merge the news from mainline into your changeset (effectively rebasing it) and then commits. This workflow is enforced without you even needing to understand it. Mainline thus collects a history of changes which you can quite easily cherry pick your way through later. For instance, suppose you want to revert an old one, say, the one before the one before last. You sync to the moment before the offending change, mark the affected files as part of the changeset, sync to the moment after and merge with "always mine". (There was something very interesting there: syncing doesn't mean having the same thing - if a file is editable (i.e. in an active changeset) it won't be clobbered by the sync but marked as due for resolving.) Now you have a changelist that undoes the offending one. Merge in the subsequent news and you have a changelist that you can plop on top of mainline to have the desired effect. At no point did we rewrite any history.
Now, supposing half way through this process, somebody runs up to you and tells you to drop everything and fix some bug. You just give your default changelist a name (a number actually) then "suspend" it, fix the bug in the now empty default changelist, commit it, and resume the named changelist. It's typical to have several changelists suspended at a time where you try different things out. It's easy and private. You get what you really want from a branch regime without the temptation to procrastinate or chicken out of merging to mainline.
I suppose it would be theoretically possible to do something similar in git, but git makes practically anything possible rather than asserting a workflow we approve of. The centralised model is a bunch of valid simplifications relative to the distributed model which is an invalid generalisation. It's so overgeneralised that it basically expects you to implement source control on top of it, as repo does.
The other thing is replication. In git, anything is possible so you have to figure it out for yourself. In perforce, you get an effectively stateless cache. The only configuration it needs to know is where the master is, and the clients can point at either the master or the cache at their discretion. That's a five minute job and it can't go wrong.
You've also got triggers and customisable forms for asserting code reviews, bugzilla references etc, and of course, you have branches for when you actually need them. It's not clearcase, but it's close, and it's dead easy to set up and maintain.
All in all, I think that if you know you're going to work in a centralised way, which everybody does, you might as well use a tool that was designed with that in mind. Git is overrated because of Linus' fearsome wit together with peoples' tendency to follow each other around like sheep, but its main raison d'etre doesn't actually stand up to common sense, and by following it, git ties its own hands with the two huge dogmas that (a) the software and (b) the data have to be the same at both client and server, and that will always make it complicated and lame at the centralised job.
Using GIT as substitute for bad code line management is common. Many of the disadvantages of Perforce are a result of bad branching strategies. The same for any other centralized tool. If you have to create a ton of branches you are doing something wrong. Why do developers need to create so many branches?
Also, why is working disconnected so important anyway? Just so someone can work on a train? That's about the only place these days you can't get a wireless connection. And even most trains have decent WiFi.
