githashsha1checksumgit-hash

How does Git compute file hashes?

The SHA1 hashes stored in the tree objects (as returned by git ls-tree) do not match the SHA1 hashes of the file content (as returned by sha1sum):

$ git cat-file blob 4716ca912495c805b94a88ef6dc3fb4aff46bf3c | sha1sum
de20247992af0f949ae8df4fa9a37e4a03d7063e  -

How does Git compute file hashes? Does it compress the content before computing the hash?

Solution

  • Git prefixes the object with "blob ", followed by the length (as a human-readable integer), followed by a NUL character

    $ echo -e 'blob 14\0Hello, World!' | shasum 8ab686eafeb1f44702738c8b0f24f2567c36da6d

    Source: http://alblue.bandlem.com/2011/08/git-tip-of-week-objects.html