Using git with multiple remote repositories
When one just isn’t good enough
Purpose
Recently I was honored to be added to the taffydb
maintainer list. This means I now need to merge changes from multiple
remote repositories. Usually this can be done using the GitHub web
interface but sometimes this is not flexible enough. Luckily, it’s rather
easy to set up your git working directory to have a different remote
repository for different branches and then merge between them. This
post shows how.
Getting set up
Below I illustrate checking out taffydb on the master branch, and then set up two alternate branches using two different source repositories.
First, let’s get the canonical taffydb repository:
git clone git@github.com:typicaljoe/taffydb.git taffydb
Now let’s enter that directory and have a look around:
cd taffydb
git remote -v
# origin git@github.com:typicaljoe/taffydb.git (fetch)
# origin git@github.com:typicaljoe/taffydb.git (push)
Let’s add our upstream branch to ltullman.
# create new branch
git checkout -b ltullman-master
# add remote repository
git remote add ltullman git@github.com:ltullman/taffydb.git
# fetch the master branch contents
git fetch ltullman master
# and now set upstream
git branch --set-upstream-to=ltullman/master
# confirm upstream branch
git rev-parse --abbrev-ref --symbolic-full-name @{u}
# ltullman/master
# confirm origin
git remote -v
# ltullman git@github.com/ltullman/taffydb.git (fetch)
# ltullman git@github.com/ltullman/taffydb.git (push)
# origin git@github.com:typicaljoe/taffydb.git (fetch)
# origin git@github.com:typicaljoe/taffydb.git (push)
At this point, we have an ltullman-master that uses the ltullman upstream repository. Let’s add another:
git checkout master
git checkout -b mmikowski-master
git remote add mmikowski git@github.com:mmikowski/taffydb.git
git fetch mmikowski master
git branch --set-upstream-to=mmikowski/master
And confirm again:
git rev-parse --abbrev-ref --symbolic-full-name @{u}
# mmikowski/master
git remote -v
# ltullman git@github.com/ltullman/taffydb.git (fetch)
# ltullman git@github.com/ltullman/taffydb.git (push)
# mmikowski git@github.com/mmikowski/taffydb.git (fetch)
# mmikowski git@github.com/mmikowski/taffydb.git (push)
# origin git@github.com:typicaljoe/taffydb.git (fetch)
# origin git@github.com:typicaljoe/taffydb.git (push)
Now we have all the sources we want. Now let’s explore what we can do!
What can we do with this?
I found that when setting up multiple upstream sources like this, we need to do a little work to get the branch to be “pristine”. For example, I found a merge conflict in my local copy of mmikowski-master. I wanted that fixed, and to match the upstream copy exactly. So I cloned another local copy and then made sure my mmikowski-master branch matched it exactly:
git checkout master-mmikowski
cd ..
git clone git@github.com/mmikowski/taffydb.git taffydb-mmikowski
# visual diff tool to merge remote master to local - copy all files
# from source (left)
kdiff3 taffydb-mmikowski taffydb
# resolve conflicts
cd taffdb
git add .
git commit -a
# And push
git push mmikowski HEAD:master
We can do the same check with ltullman. Now we can cherry-pick changes from a branch and merge them into master. In the example below, I merged over my regression tests but left other changes alone as I didn’t feel they were well-tested enough.
checkout master
git difftool mmikowski-master taffy-test.html
When to use this
Pull-requests that can be resolved from the GitHub web interface are always preferred if possible. However, sometimes circumstances require more nuanced merging, and this is where having remote repositories for each branch is very, very handy.
Cheers, Mike