[yes_or_gnome]

Based on my own research, it appears that the first git tag was created before the first git commit.

The first tag (?) points to a tree.

  $ git cat-file -p v2.6.11-tree
  object c39ae07f393806ccf406ef966e9a15afc43cc36a
  type tree
  tag v2.6.11-tree

  This is the 2.6.11 tree object.

  NOTE! There's no commit for this, since it happened before I started with git.
  Eventually we'll import some sort of history, and that should tie this tree
  object up to a real commit. In the meantime, this acts as an anchor point for
  doing diffs etc under git.
  -----BEGIN PGP SIGNATURE-----
  Version: GnuPG v1.2.4 (GNU/Linux)

  iD8DBQBCeV/eF3YsRnbiHLsRAl+SAKCVp8lVXwpUhMEvy8N5jVBd16UCmACeOtP6
  KLMHist5yj0sw1E4hDTyQa0=
  =/bIK
  -----END PGP SIGNATURE-----

First commit

  $ git cat-file -p v2.6.12-rc2
  object 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
  type commit
  tag v2.6.12-rc2

  Linux v2.6.12-rc2 release
  -----BEGIN PGP SIGNATURE-----
  Version: GnuPG v1.2.4 (GNU/Linux)

  iD8DBQBCbW8ZF3YsRnbiHLsRAgFRAKCq/TkuDaEombFABkPqYgGCgWN2lQCcC0qc
  wznDbFU45A54dZC8RZ5JxyE=
  =ESRP
  -----END PGP SIGNATURE-----

Unfortunately, I don't think I can confirm my suspicion using git alone. Maybe if I look at some mailing lists around July/August 2005 I could get a more accurate confirmation.

This is due to the fact that those tags pre-date the tagger header which came a short while later.

  $ git cat-file -p v2.6.13
  object 02b3e4e2d71b6058ec11cc01c72ac651eb3ded2b
  type commit
  tag v2.6.13
  tagger Linus Torvalds <[e-mail]> 1125272548 -0700

  Linux 2.6.13 release
  -----BEGIN PGP SIGNATURE-----
  Version: GnuPG v1.4.1 (GNU/Linux)

  iD8DBQBDEkvwF3YsRnbiHLsRAp5tAKCEK1XmOropxvWp+k9eiTcafNMXXACcDAVb
  +hOwdKI+bi84SSNNSGnSXGg=
  =cnNS
  -----END PGP SIGNATURE-----

Edit:

Just to reenforce the "First Commit" claim, here's the rev-list for the commit and the commit contents. (Notice it has no "parent" commit.

  $ git rev-list 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
  1da177e4c3f41524e886b7f1b8a0c1fc7321cac2

  $ git dump 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
  tree 0bba044c4ce775e45a88a51686b5d9f90697ea9d
  author Linus Torvalds <[e-mail]> 1113690036 -0700
  committer Linus Torvalds <[e-mail]> 1113690036 -0700

  Linux-2.6.12-rc2

  Initial git repository build. I'm not bothering with the full history,
  even though we have it. We can create a separate "historical" git
  archive of that later if we want to, and in the meantime it's about
  3.2GB when imported into git - space that would just make the early
  git days unnecessarily complicated, when we don't have a lot of good
  infrastructure for it.

  Let it rip!