Freezing a Git branch
Christopher is right, tagging will help you do this. I recommend deleting the branch name too to make it a little harder for someone to checkout the branch and make edits.
First, merge the branch into develop
git checkout develop
git merge --no-ff feature_1
Then checkout the branch
git checkout feature_1
Then create a tag, with a comment.
git tag -a -m "Freezing a feature branch that fixes.." feature_1_frozen
Then delete the branch
git checkout develop
git branch -d feature_1
After doing this, you won't be able to checkout the branch by name. Instead you'll be able to checkout the tag by name, this will put you into a detached head state which will deter changes to the code.
Now to wrap things up and sync with origin...
Push the update and new tag
git push --tags origin develop
Delete the remote feature branch
git push origin :feature_1
Just tag it.
git tag -a frozen -m "Feature branch frozen here."
git push <remote> frozen
Sure, someone could come along later and push to the branch, but the tag shouldn't change unless it's forcibly overrode. You could configure your remote to reject force pushes if you're concerned about it, or even sign the tags with a GPG key to ensure authenticity.
Getting the state of the feature branch when it was frozen is as simple as git checkout frozen
. Developers can branch from this point at will using one command: git checkout -B <new_branch> frozen
.