Q: submodules and detached HEAD

Hi!

I'm rather new to submodules, and I have a question on something I don't understand (git-2.12.3 from SLES12): I had checked out tag v0.0.1 of my submodule. When checking the status, I see:

iptables> git status
HEAD detached at v0.0.1
nothing to commit, working tree clean
iptables> git checkout v0.0.1
HEAD is now at b23fbdc... .version: 0.0.1
iptables> git checkout v0.0.2
Previous HEAD position was b23fbdc... .version: 0.0.1
HEAD is now at 5af0df5... v0.0.2: Fix issue with "xtables lock"
/iptables> git status
HEAD detached at v0.0.2
nothing to commit, working tree clean
iptables> git branch
* (HEAD detached at v0.0.2)
  master

git reflog says: 5af0df5 HEAD@{0}: checkout: moving from b23fbdc0e18e570a4d9ec4cb8826afc82e2e0b64 to v0.0.2 b23fbdc HEAD@{1}: checkout: moving from ec7dd70b59e039b49bb478a3134b713a2b0a279c to v0.0.1 ec7dd70 HEAD@{2}: checkout: moving from master to v0.0

Config submodule.iptables.branch is not set.

Who can explain?

Regards, Ulrich