What can cause git commit to disappear?

Question

With git, I know that rebasing will recreate the commits that are being rebased, thus creating completely new sha values for each commit.

Is rebasing the only way to destroy existing sha values ?

Answer 1

There are many ways to do it as well which are not described here as well.

• checkout / revert /reflog / reset
  Read it all here: How to move HEAD back to a previous location? (Detached head)

• git filter-branch
  This command alter your history and allow you to delete commits as well.

• git rebase / git rebase -i HEAD~x
  Here you can squash several commits into a new commit

• BFG Repo-Cleaner Removes large or troublesome blobs like git-filter-branch does, but faster.

BFG Repo-Cleaner