Git checkout of commit# is taking me to a different commit#

Question

So, something weird that I hadn't encountered before.

$ git checkout fb4b6581d36a522e092491d1dc5f49cb96ab7a3e
Note: checking out 'fb4b6581d36a522e092491d1dc5f49cb96ab7a3e'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b <new-branch-name>

HEAD is now at 8a74070...

Basically my question is, if I checked out fb4b6581, why is HEAD now at 8a74070? My basic Git knowledge is not enough to fully understand what's going on. Let me know if I should add more information to this question, this is the gist of the issue I'm seeing.

Also, note that if I do git log, I do not see fb4b6581 anywhere, but I do see 8a74070, which adds to my confusion.

Thank you

Answer 1

This means that the Git object with ID fb4b6581d36a522e092491d1dc5f49cb96ab7a3e is a tag object (an annotated tag).

You can see it with:

$ git cat-file -t fb4b6581d36a522e092491d1dc5f49cb96ab7a3e

which will print the object's type, and:

$ git cat-file -p fb4b6581d36a522e092491d1dc5f49cb96ab7a3e

which will print the raw tag contents directly. The git show command will show the tag's contents first, and then the commit to which the tag points, which is this other object 8a74070....