If a git tag changes on remote, a git fetch does not update it locally. Is this a bug?

Make sure you fetch all the tags (through git fetch --tags), to get all the tags and not just ones referencing commits reachable from the branch heads.

Those (fetched) tags are annotated ones (and usually not lightweight), and if you add deleted one on the local repo, they will just pop back after the fetch.

However, if you have deleted a lightweight one, then you need to recreate it locally: a lightweight tag isn't usually pushed or fetched to/from a remote repo.

Note that starting git 1.9/2.0 (Q1 2014), git fetch --tags will fetch everything (like git fetch), plus the tags. See "Does “git fetch --tags” include “git fetch”?".

Again, fetch "everything" means annotated and lightweight (if those lightweight tags were previously pushed).

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As noted below in biocyberman's answer, if you want to fetch tags from all remotes (not just the default remote named 'origin'), you need to add the --all option.

git fetch --tags --all

Previous to git 2.30, the right way seemed to be:

  git fetch origin --tags --force

You should avoid to have a branch with the same tag name, because the checkout prioritizes the branch and you can feel like the tag was not updated. Maybe git should have a warning in this case, something like:

You have updated a tag that differs now from a branch of the same name. The reference to "tagname" became ambiguous.

What you have said is the right way and that is what the git tag manual recommends ( actually, it says, don't change the tags on the remote repo unless the world is coming to an end):

git tag -d X
git fetch origin tag X