A nice and simple question - is the function of "git fetch" a strict sub-set of git fetch --tags?
I.e. if I run git fetch --tags, is there ever a reason to immediately run git fetch straight afterward?
What about git pull and git pull --tags? Same situation?
Note: this answer is only valid for git v1.8 and older.
Most of this has been said in the other answers and comments, but here's a concise explanation:
git fetch fetches all branch heads (or all specified by the remote.fetch config option), all commits necessary for them, and all tags which are reachable from these branches. In most cases, all tags are reachable in this way.git fetch --tags fetches all tags, all commits necessary for them. It will not update branch heads, even if they are reachable from the tags which were fetched.Summary: If you really want to be totally up to date, using only fetch, you must do both.
It's also not "twice as slow" unless you mean in terms of typing on the command-line, in which case aliases solve your problem. There is essentially no overhead in making the two requests, since they are asking for different information.
I'm going to answer this myself.
I've determined that there is a difference. "git fetch --tags" might bring in all the tags, but it doesn't bring in any new commits!
Turns out one has to do this to be totally "up to date", i.e. replicated a "git pull" without the merge:
$ git fetch --tags
$ git fetch
This is a shame, because it's twice as slow. If only "git fetch" had an option to do what it normally does and bring in all the tags.
In most situations, git fetch should do what you want, which is 'get anything new from the remote repository and put it in your local copy without merging to your local branches'. git fetch --tags does exactly that, except that it doesn't get anything except new tags.
In that sense, git fetch --tags is in no way a superset of git fetch. It is in fact exactly the opposite.
git pull, of course, is nothing but a wrapper for a git fetch <thisrefspec>; git merge. It's recommended that you get used to doing manual git fetching and git mergeing before you make the jump to git pull simply because it helps you understand what git pull is doing in the first place.
That being said, the relationship is exactly the same as with git fetch. git pull is the superset of git pull --tags.
git fetch upstream --tags
works just fine, it will only get new tags and will not get any other code base.