Tags auto fetched by "git fetch origin" but not "git fetch origin main"

[Yukai Chou <muzimuzhi@xxxxxxxxx>]

In using `git fetch [<options>] [<repository> [<refspec>…]]`,
- when a branch is specified as <refspec>, no tags are fetched automatically;
- when no <refspec>s are specified, tags are fetched automatically.

This reproduces with both glob (`+refs/heads/*:refs/remotes/origin/*`)
or restricted (`+refs/heads/main:refs/remotes/origin/main`)
`remote.<name>.fetch`.