How to hide remote branches without deleting them from remote

You can do this using the --exclude option:

git log --graph --oneline --exclude=refs/remotes/* --all

Note that the --exclude option must appear before the --all option. See the git log documentation for further information.

You can use

git log --graph --oneline --tags --branches

Add HEAD if you are on a detached head.

The options --tags, --branches, --remotes are quite versatile when combined with --exclude. For example, I have many branches named wip/foo, wip/bar that contain work in progress. I commonly use

gitk --exclude=wip/* --branches ^master

to see all branches that are not yet merged into master, but without cluttering the list with work-in-progress.