Some workflows require that one or more branches of development on one machine be replicated on another machine, but the two machines cannot be directly connected, and therefore the interactive Git protocols (git, ssh, http) cannot be used. This command provides support for git fetch and git pull to operate by packaging objects and references in an archive at the originating machine, then importing those into another repository using git fetch and git pull after moving the archive by some means (e.g., by sneakernet). As no direct connection between the repositories exists, the user must specify a basis for the bundle that is held by the destination repository: the bundle assumes that all objects in the basis are already in the destination repository.
git bundle will only package references that are shown by git show-ref: this includes heads, tags, and remote heads. References such as master~1 cannot be packaged, but are perfectly suitable for defining the basis. More than one reference may be packaged, and more than one basis can be specified. The objects packaged are those not contained in the union of the given bases. Each basis can be specified explicitly (e.g. ^master~10), or implicitly (e.g. master~10..master, --since=10.days.ago master).
It is very important that the basis used be held by the destination. It is okay to err on the side of caution, causing the bundle file to contain objects already in the destination, as these are ignored when unpacking at the destination.
Assume you want to transfer the history from a repository R1 on machine A to another repository R2 on machine B. For whatever reason, direct connection between A and B is not allowed, but we can move data from A to B via some mechanism (CD, email, etc.). We want to update R2 with development made on the branch master in R1.
To bootstrap the process, you can first create a bundle that does not have any basis. You can use a tag to remember up to what commit you last processed, in order to make it easy to later update the other repository with an incremental bundle:
machineA$ cd R1 machineA$ git bundle create file.bundle master machineA$ git tag -f lastR2bundle master
Then you transfer file.bundle to the target machine B. Because this bundle does not require any existing object to be extracted, you can create a new repository on machine B by cloning from it:
machineB$ git clone -b master /home/me/tmp/file.bundle R2
This will define a remote called "origin" in the resulting repository that lets you fetch and pull from the bundle. The $GIT_DIR/config file in R2 will have an entry like this:
[remote "origin"] url = /home/me/tmp/file.bundle fetch = refs/heads/*:refs/remotes/origin/*
To update the resulting mine.git repository, you can fetch or pull after replacing the bundle stored at /home/me/tmp/file.bundle with incremental updates.
After working some more in the original repository, you can create an incremental bundle to update the other repository:
machineA$ cd R1 machineA$ git bundle create file.bundle lastR2bundle..master machineA$ git tag -f lastR2bundle master
You then transfer the bundle to the other machine to replace /home/me/tmp/file.bundle, and pull from it.
machineB$ cd R2 machineB$ git pull
If you know up to what commit the intended recipient repository should have the necessary objects, you can use that knowledge to specify the basis, giving a cut-off point to limit the revisions and objects that go in the resulting bundle. The previous example used the lastR2bundle tag for this purpose, but you can use any other options that you would give to the git-log(1) command. Here are more examples:
You can use a tag that is present in both:
$ git bundle create mybundle v1.0.0..master
You can use a basis based on time:
$ git bundle create mybundle --since=10.days master
You can use the number of commits:
$ git bundle create mybundle -10 master
You can run git-bundle verify to see if you can extract from a bundle that was created with a basis:
$ git bundle verify mybundle
This will list what commits you must have in order to extract from the bundle and will error out if you do not have them.
A bundle from a recipient repository's point of view is just like a regular repository which it fetches or pulls from. You can, for example, map references when fetching:
$ git fetch mybundle master:localRef
You can also see what references it offers:
$ git ls-remote mybundle