Introduction and Overview of Steps:
In order to migrate from Laravel 4.2 to Laravel 5 when it initially came out, I created a new branch and began to work through the uprade. My intention initially was to merge the branch back into master, but never got around to it. After so much time (and something like 500 commits later) I decided to just make the Laravel 5 branch (called 'new_master' below) the new master branch using the following steps:
git checkout new_master
git merge --strategy=ours --no-commit master
git commit -am 'changing branch "new_master" to "master"'
git checkout master
git merge new_master
Step 1 - Checkout the 'new_master' Branch
ubuntu /var/www/test $ sudo git checkout new_master
Step 2 - Merge
ubuntu /var/www/test $ sudo git merge --strategy=ours --no-commit master
Automatic merge went well; stopped before committing as requested
Step 3 - Add a Commit Including a Helpful Message
ubuntu /var/www/test $ sudo git commit -am 'changing branch "new_master" to "master"'
[new_master 5b19bcf] changing branch "new_master" to "master"
Step 4 - Checkout 'master' Branch
ubuntu /var/www/test $ sudo git checkout master
Switched to branch 'master'
Your branch is up-to-date with 'origin/master'.
Step 5 - Merge 'new_master' Branch
ubuntu /var/www/test $ sudo git merge new_master
Step 6 - Check Git Status
ubuntu /var/www/test $ git status
On branch master
Your branch is ahead of 'origin/master' by 544 commits.
(use "git push" to publish your local commits)
nothing to commit, working directory clean
Step 7 - Push to Branch 'master'
ubuntu /var/www/test $ sudo git push origin master
Counting objects: 1, done.
Writing objects: 100% (1/1), 238 bytes | 0 bytes/s, done.
Total 1 (delta 0), reused 0 (delta 0)
To git@github.com:test/test.git
fef1e53..5b19bcf master -> master
After completing the above steps successfully in a test environment, all that was left to do on the production server was to checkout the master branch with a `git checkout master` and run a single `git pull origin master`.