+
+
+Get an older version of a file
+------------------------------
+
+```sh
+git cat-file -p $COMMIT_DIGEST:$FILE_PATH
+```
+
+
+Splitting a commit
+------------------
+
+From [docs](https://git-scm.com/docs/git-rebase#_splitting_commits):
+
+- Start an interactive rebase with `git rebase -i <commit>^`, where `<commit>`
+ is the commit you want to split.
+- Mark the commit you want to split with the action "edit".
+- When it comes to editing that commit, execute `git reset HEAD^`. The effect
+ is that the HEAD is rewound by one, and the index follows suit. However, the
+ working tree stays the same.
+- Now add the changes to the index that you want to have in the first commit
+ (`git add`)
+- Commit the now-current index with whatever commit message is appropriate now.
+- Repeat the last two steps until your working tree is clean.
+- Continue the rebase with `git rebase --continue`.
+
+
+Merge 2 repos
+-------------
+
+```sh
+$ ls -1
+repo_A
+repo_B
+$ cd repo_B
+$ git remote add repo_A ../repo_A
+$ git fetch repo_A --tags
+$ git merge --allow-unrelated-histories repo_A/$BRANCH
+$ git remote remove repo_A
+```