FR: Promote tag fetching strategy to a JJ option (additionally)

[Vampire]

On jj git clone and jj git remote add you can use --fetch-tags to configure which tags are fetched along.

But as far as I have seen these options just set the tagOpt option on the remote in the Git config.
I did not find a way to change that later on without falling back to using Git.
Except for removing the remote using jj git remote removeand readding it with jj git remote add that is.

It would be nice if this would be a regular jj config that you could also set in the --user file and that just gives --tags or --no-tags option to the fetch as appropriate.

I usually always want all tags to be fetched.
And if I would not want it for a repo, the repo config file could override it.

Up to now with Git I had an alias that fetched from all remotes with all tags and pruning remote tracking branches.
Fetching from all remotes is configurable with JJ, pruning remote tracking branches is done automatically, so the only missing thing is the tag fetching strategy.
And as I always used that fetching alias, I also never bothered to set the tagOpt on the remotes of the clones that I now do jj git init in.

Of course you might want to still configure it per remote,
so if the tagOpt option is set for some remote, it could still override the repo level config which overrides the user level config.

[yuja]

In the context of #7528, I'm thinking of reimplementing remote tag handling. The current --fetch-tags might be deprecated because I don't think --fetch-tags=included can be simulated by using explicit refs/tags/*:<dest> refspec.

[Vampire]

Well, with such a refspec you would probably then have to filter manually which is in the ancestry of fetched revs, shouldn't be too hard I guess.

But even if only fetch and no-fetch is supported, I think it would make sense to have a user-level setting, a repo-level override, and a remote-level override what to do.

[yuja]

Perhaps, tagOpt in .git/config won't be respected, and tags will be handled in the same way as bookmarks/branches. I don't remember there's a default for bookmarks, but we'll add a similar jj configuration for tags.