How to deal with Git "Could not read" error

Question

I am getting this error in my git repository:

22:09:15 $ git status
# On branch master
error: Could not read 8124cc15c63be92d534e4cdfa33c38d54deee122
error: unable to read tree object HEAD
nothing to commit (working directory clean)

A Google search for error: unable to read tree object HEAD doesn't result in much help, this error seems to be very rare. I am not sure how to deal with it. Could it be a hard drive failure?

Edit: The output of git fsck is the following:

broken link from  commit 607328dc80e4901a55b95c683d4fbf43e6df28bf
              to    tree 8124cc15c63be92d534e4cdfa33c38d54deee122
missing tree 8124cc15c63be92d534e4cdfa33c38d54deee122
dangling tree 56b5d4a5e429d251582ec927bca7ef1225510c41
dangling tree 0259d2d38b18b6136bb6070fb41faf3624453cc6

Answer 1

On a "broken link" message, you could follow the GitFaq recommendations:

• back up all your state so that anything you do is re-doable if you corrupt things more!
• explode any corrupt pack-files
  • See "man git-unpack-objects", and in particular the "-r" flag.
    Also, please realize that it only unpacks objects that aren't already available, so you need to move the pack-file away from its normal location first (otherwise git-unpack-objects will find all objects that are in the pack-file in the pack-file itself, and not unpack anything at all)
• replace any broken and/or missing objects
  • This is the challenging part.
    Sometimes (hopefully often!) you can find the missing objects in other copies of the repositories.
    At other times, you may need to try to find the data some other way (for example, maybe your checked-out copy contains the file content that when hashed will be the missing object?).
• make sure everything is happy with "git fsck --full"
• repack everything to get back to an efficient state again

---

Notes:

• missing objects can also be related to alternate (when you share objects between repositories) with git alternates (even though that can be risky).
• The JGit/Egit eclipse plugin is also known to have a few issues.
  (Update February 2012: those plugins have come a long way and are now quite stable)

Update July 2016 (7 years laters), with Git 2.10 soon to be released, you now have:

git fsck --name-objects

It helps naming the origin of those broken links

See "How to fix git error broken link from tree to tree?" for more.