While the Git gc command optimizes and removes dead objects from the repo, the fsck command reports on repo problems.

git fsck

I used to run it with the –full option, but this is now the default.  I typically run it as is or with the –tags option.  You may occasionally appreciate the –strict and –verbose options as well.

Note – it is not a repair tool.  It will report any missing or corrupted data/git objects, but not repair them.  Your backups, central repo, or teammates’ repos are your recovery options.