On: Announcing the first SHA-1 collision

[kinkrtyavimoodh]

No, a commit is not the SHA-1 of the diff. The fundamental object model of Git does not store diffs, it stores the actual state of the source tree as represented by a commit. For instance, here's a commit file [1]—

  $ git cat-file -p fdf4fc3
  tree d8329fc1cc938780ffdd9f94e0d364e0ea74f579
  author Scott Chacon <schacon@gmail.com> 1243040974 -0700
  committer Scott Chacon <schacon@gmail.com> 1243040974 -0700

  first commit

A commit object just points to the tree object (in turn, another SHA-1, this time of the complete directory listing) and other meta information such as author name etc.

[1] https://git-scm.com/book/en/v2/Git-Internals-Git-Objects

[anilgulecha → kinkrtyavimoodh]

Correct -- I was being terse: the commit is a function of the changes going in (and metadata like time, authorship).

Details: https://gist.github.com/masak/2415865

[chronial → anilgulecha]

That is not correct and also not supported by your link. A git commit does not contain any changes. It is always a full sapshot of the repo state.

To have any kind of concept of "change", you need two gït commits. Just like a simple text file.

[0x0 → anilgulecha]

I'm not really talking about entire git commits, but just single files (blobs) within any commit/tree/repository