Update ERPNext without losing changes

[anupd]

I ran

bench update

I got the following message:

Cannot proceed with update: You have local changes in app “frappe” that are not committed.
Here are your choices:

1. Merge the frappe app manually with “git pull” / “git pull --rebase” and fix conflicts.
2. Temporarily remove your changes with “git stash” or discard them completely
   with “bench update --reset” or for individual repositries “git reset --hard”
3. If your changes are helpful for others, send in a pull request via GitHub and
   wait for them to be merged in the core.

This is exactly what I wanted to avoid. How can I solve the issue without removing my customizations ? I am not an expert on GIT.
I also read the documentationson git stash. But I am not sure if I should proceed. And how should I proceed ?

Update:

I found the following steps:

@ci2016

1. Go to the directory, either frappe-bench/apps/erpnext or frappe-bench/apps/frappe
2. Type git status
3. Check the list of the untracked files. There might be files, which do or don’t belong there.
4. Type git add --all to track those files
5. Type git stash
6. Run bench update
7. It should run successfully, if not, start over with 1. and repeat for the other directory

On this point you’re already done, but you may want to apply your changes, which you stashed. So continue with 8. if you stashed things, which you consider important.

8 . While you’re still in the folder, either frappe-bench/apps/erpnext or frappe-bench/apps/frappe type git stash apply

Your changes will be applied again, but on the next run, you will run into the same issue like you had before.

Are these safe to run ?