no way to give only access to public repositories while authenticating with github about bloop HOT 2 CLOSED

I was now installing bloop myself and ran into similar concerns.
To limit to public repos, it seems to me you can use the public_repo scope (or maybe even no scope at all might work?).
I haven't tried it, but from the docs page it seems that's the case.

My other concern is the write access given. I'm a bit reticent to giving write access to my repos just to try out an app. Maybe there are some features in bloop that require write access? I'm not sure, because I haven't yet tried it due to this.

It seems there is no scope for read-only access to private repos (see jollygoodcode/jollygoodcode.github.io#6), but there is a newish feature for setting permissions granularly (see the blog post).
Although it doesn't seem very user-friendly; as far as I can tell you can't get them in an oauth workflow, the user would need to create the token with the correct permissions and give it to bloop.

It would be cool if you implemented bringing your own personal access token as an alternative to oauth :)

from bloop.

Unfortunately, we can't change that. We need access to your repos to be able to sync them. We use a standard GitHub oauth scopes, mainly 'repo' scope (docs). I don't see any easy way to limit it to only public repos. If you do, please share.
In any case, we don't sync any repos until you specify which ones you want to index. You can pick only those that are public manually from the list. We don't share a list of your repos with anybody and need it only to show you a select menu.

from bloop.