我应该使用Git分支来存储不相关的代码吗？

Like you mentioned, you can accomplish this with orphan branches.

git checkout --orphan script-branch
git reset --hard
touch my-script.sh
git add my-script.sh
git commit -m 'Script commit'

Now if you do a git log, you will only see 'Script commit' in the history.

There is nothing inherently wrong with this approach, but there are some pros and cons:

Pros:

Low overhead: Your new branches are easily accessible by everyone who already has access to your repo. All you have to do is checkout the branch and you're ready to go.

Separation: Since your scripts are in a separate branch, they can be maintained separately and have their own separate git history.

Cons:

Unusual organization: Typically people expect branches to be a modified version of the master branch. You will need to clarify your scheme to other developers.

Can't access both at the same time: You will not be able to access your scripts while you have master checked out and vice-versa. You can solve this by cloning your repo twice, but that may complicate things.

Heavy clone: You mentioned that a separate branch will save you from having to clone the whole repository, but you will do that anyway. If you run clone normally, git will clone every branch including your master branch regardless of which branch you have checked out. You can use the --single-branch flag to only clone one branch, but that would somewhat nullify the utility of having the branch in the same repo.

Alternatives:

Include your scripts in a directory in your master branch. Yes, this means you have to clone the entire repository just to get the scripts. But if the scripts are related to the code in your master branch, this is the simplest and most standard solution.

Create a single new repo just for your scripts. You can then use directories to group related scripts. This saves you the overhead of having a separate repo for every set of scripts, but still allows you to clone it separately.