git: merge changes from main repo in code.google.com

Question

Let's say that I've created a clone http://code.google.com/r/kkowalczyk-leveldb of http://code.google.com/p/leveldb using web interface on code.google.com

Since the time I created my clone, there were changes made to http://code.google.com/p/leveldb and I would like to merge them to my clone, preferably preserving history (i.e. I could merge them manually using a diff/merge tool, but that doesn't preserve git history).

What are the magic commands to perform such merge?

Preferably please provide the complete commands. I imagine it'll involve some combination of git fetch and git merge and remote-tracking branches etc. My problem is not that I can't read man pages for git fetch or merge, I just don't understand them.

Update:

Given Lazy Badger's comment below, I've solved half of the issue:

git remote add original https://code.google.com/p/leveldb/

Creates something called 'original' pointing to the source. I can then do:

git pull original master

Which fetches and merges changes from original into my branch master. I would, however, to do it in 2 separate steps: as git fetch and git merge $something to merge into my current branch.

However, after git fetch original, I don't know what $something would be. When I do git branch -a, I don't see anything related to my remote original thingy.

What complicates things is that there are 3 branches in original as well.

So, where do data fetched from original go and how should I refer to it in my git merge $something?

Answer 1

You already found how to add another remote and pull directly from it:

git remote add original https://code.google.com/p/leveldb/
git pull original master

If you want to do the fetch and merge separately (instead of a single pull command; maybe because you want to inspect what changed before merging it), then you can do that like this:

git fetch original         # update refs/remotes/original/*
git merge original/master  # merge refs/remotes/original/master

You might inspect the changes before merging with this command:

git log --reverse -p original/master@{1}..original/master@{0}

Instead of using the above reflog-based revision specification, you could also just copy-and-paste the oldhash..newhash revision specification that was output during the fetch.

---

Technically, git pull remote branch is closer to this pair of commands:

git fetch remote-or-url branch  # grab remote branch and put it in FETCH_HEAD
git merge FETCH_HEAD            # merge it

but this pair (and thus also pulling with both a remote and a branch specified) is usually not as nice since it does not update the remote-tracking branches (refs/remotes/original/*). The remote+branch invocations of fetch and pull are useful for one-off merges from repositories for which you do not particularly want to keep a full set of remote-tracking branches (i.e. fetching/pulling a merge request from a minor/rare contributor).

Answer 2

You can add multiple remotes to a single repository. Once you've got the second remote, you can simply push the changes of the first to the second. For example:

git clone <google_URI>
cd <projdir>
git remote add github <github_URI>
git push github master