2. Git Basics
7. Git Tools
10. Git Internals
7.12 Git Tools - Bundling
Though we’ve covered the common ways to transfer Git data over a network (HTTP, SSH, etc), there is actually one more way to do so that is not commonly used but can actually be quite useful.
Git is capable of “bundling” it’s data into a single file. This can be useful in various scenarios. Maybe your network is down and you want to send changes to your co-workers. Perhaps you’re working somewhere offsite and don’t have access to the local network for security reasons. Maybe your wireless/ethernet card just broke. Maybe you don’t have access to a shared server for the moment, you want to email someone updates and you don’t want to transfer 40 commits via
This is where the
git bundle command can be helpful. The
bundle command will package up everything that would normally be pushed over the wire with a
git push command into a binary file that you can email to someone or put on a flash drive, then unbundle into another repository.
Let’s see a simple example. Let’s say you have a repository with two commits:
$ git log commit 9a466c572fe88b195efd356c3f2bbeccdb504102 Author: Scott Chacon <email@example.com> Date: Wed Mar 10 07:34:10 2010 -0800 second commit commit b1ec3248f39900d2a406049d762aa68e9641be25 Author: Scott Chacon <firstname.lastname@example.org> Date: Wed Mar 10 07:34:01 2010 -0800 first commit
If you want to send that repository to someone and you don’t have access to a repository to push to, or simply don’t want to set one up, you can bundle it with
git bundle create.
$ git bundle create repo.bundle HEAD master Counting objects: 6, done. Delta compression using up to 2 threads. Compressing objects: 100% (2/2), done. Writing objects: 100% (6/6), 441 bytes, done. Total 6 (delta 0), reused 0 (delta 0)
Now you have a file named
repo.bundle that has all the data needed to re-create the repository’s
master branch. With the
bundle command you need to list out every reference or specific range of commits that you want to be included. If you intend for this to be cloned somewhere else, you should add HEAD as a reference as well as we’ve done here.
You can email this
repo.bundle file to someone else, or put it on a USB drive and walk it over.
On the other side, say you are sent this
repo.bundle file and want to work on the project. You can clone from the binary file into a directory, much like you would from a URL.
$ git clone repo.bundle repo Initialized empty Git repository in /private/tmp/bundle/repo/.git/ $ cd repo $ git log --oneline 9a466c5 second commit b1ec324 first commit
If you don’t include HEAD in the references, you have to also specify
-b master or whatever branch is included because otherwise it won’t know what branch to check out.
Now let’s say you do three commits on it and want to send the new commits back via a bundle on a USB stick or email.
$ git log --oneline 71b84da last commit - second repo c99cf5b fourth commit - second repo 7011d3d third commit - second repo 9a466c5 second commit b1ec324 first commit
First we need to determine the range of commits we want to include in the bundle. Unlike the network protocols which figure out the minimum set of data to transfer over the network for us, we’ll have to figure this out manually. Now, you could just do the same thing and bundle the entire repository, which will work, but it’s better to just bundle up the difference - just the three commits we just made locally.
In order to do that, you’ll have to calculate the difference. As we described in Commit Ranges, you can specify a range of commits in a number of ways. To get the three commits that we have in our master branch that weren’t in the branch we originally cloned, we can use something like
master ^origin/master. You can test that with the
$ git log --oneline master ^origin/master 71b84da last commit - second repo c99cf5b fourth commit - second repo 7011d3d third commit - second repo
So now that we have the list of commits we want to include in the bundle, let’s bundle them up. We do that with the
git bundle create command, giving it a filename we want our bundle to be and the range of commits we want to go into it.
$ git bundle create commits.bundle master ^9a466c5 Counting objects: 11, done. Delta compression using up to 2 threads. Compressing objects: 100% (3/3), done. Writing objects: 100% (9/9), 775 bytes, done. Total 9 (delta 0), reused 0 (delta 0)
Now we have a
commits.bundle file in our directory. If we take that and send it to our partner, she can then import it into the original repository, even if more work has been done there in the meantime.
When she gets the bundle, she can inspect it to see what it contains before she imports it into her repository. The first command is the
bundle verify command that will make sure the file is actually a valid Git bundle and that you have all the neccesary ancestors to reconstitute it properly.
$ git bundle verify ../commits.bundle The bundle contains 1 ref 71b84daaf49abed142a373b6e5c59a22dc6560dc refs/heads/master The bundle requires these 1 ref 9a466c572fe88b195efd356c3f2bbeccdb504102 second commit ../commits.bundle is okay
If the bundler had created a bundle of just the last two commits they had done, rather than all three, the original repository would not be able to import it, since it is missing requisite history. The
verify command would have looked like this instead:
$ git bundle verify ../commits-bad.bundle error: Repository lacks these prerequisite commits: error: 7011d3d8fc200abe0ad561c011c3852a4b7bbe95 third commit - second repo
However, our first bundle is valid, so we can fetch in commits from it. If you want to see what branches are in the bundle that can be imported, there is also a command to just list the heads:
$ git bundle list-heads ../commits.bundle 71b84daaf49abed142a373b6e5c59a22dc6560dc refs/heads/master
verify sub-command will tell you the heads as well. The point is to see what can be pulled in, so you can use the
pull commands to import commits from this bundle. Here we’ll fetch the master branch of the bundle to a branch named other-master in our repository:
$ git fetch ../commits.bundle master:other-master From ../commits.bundle * [new branch] master -> other-master
Now we can see that we have the imported commits on the other-master branch as well as any commits we’ve done in the meantime in our own master branch.
$ git log --oneline --decorate --graph --all * 8255d41 (HEAD, master) third commit - first repo | * 71b84da (other-master) last commit - second repo | * c99cf5b fourth commit - second repo | * 7011d3d third commit - second repo |/ * 9a466c5 second commit * b1ec324 first commit
git bundle can be really useful for sharing or doing network-type operations when you don’t have the proper network or shared repository to do so.