Git and GitHub Cheat Sheet

1 Overview

1.1 Format

Commands are written in the following format.

```shell
git ... # Comment.
```

2 General

git commit -m "Add new xyz feature"
git push

3 Destructive Actions

3.1 Reset

3.1.1 Move to Commit

To revert HEAD to a previous commit without the commit ID (also to Force Revert commits).

git reset --hard HEAD^  # Reset to 1 commit back, add `^` for each additional commit.
git reset --hard <commit_hash>  # Reset to specific commit hash.

3.1.2 Move to Branch Tip Reference

This resets the current branch's tip to the specified branch. In other words, it makes the current branch point to the same commit as the target branch.

git reset --hard origin/<branch>  # Target to match head to remote branch.
git reset --hard <branch>  # Target to match head to local branch.

3.1.3 Flags

--soft: Does not touch the index file or the working tree, but resets the head to . Changes from onwards are preserved in the working directory and as staged changes.

--mixed: Resets the index but not the working tree (i.e., the changed files are preserved but not marked for commit) and reports what has not been updated. This is the default action if no mode is specified.

--hard: Resets the index and working tree. Any changes to tracked files in the working tree since are discarded.

--merge: Resets the index and updates the files in the working tree that are different between and HEAD, but keeps those which are different between the index and working tree (i.e., which have changes which have not been added). If a merge conflict arises, it needs to be resolved manually.

--keep: Resets index entries and updates files in the working tree that are different between and HEAD. If a file that is different between and the index has unstaged changes, reset is aborted.

3.2 Amend

Amend changes the most recent commit. A new commit is created and the old is removed. Thus, this is a destructive action.

git add ./<changes> # Stage the changes to add.
git commit --amend -m <"New commit message">

3.2.1 Flags

--no-edit: Keeps the same commit message as before. The commit message flag -m and the argument can be skipped.

3.3 Pushing Destructive Changes

⚠️ Danger zone!

git push -f

4 Submodule

4.1 Add Submodule

git submodule add <remote_origin> <destination_path>

• <destination_path> is optional.

When adding a Git submodule, the new submodule will automatically be staged. To commit and push, standard procedure can be followed.

4.1.1 Results (.gitmodules)

Following a new Git submodule commit, multiple actions will be performed automatically:

1. A new directory is created in the repository named after the submodule added.
2. A .gitmodules file is created in the Git repository.
   • Contains the references to the remote repositories acting as submodules.
3. .git/config is modified to include the added submodule.

4.2 Clone with Submodules

git clone --recursive <https://github.com/github/.github>  # GitHub repo.

4.3 Fetch Submodule Commits

cd repository/submodule # Enter submodule directory.
git fetch

4.4 Pull Submodule

git submodule update # --init --recursive

4.5 Update Submodule

git submodule update # --remote --merge

• If you do not use the –remote flag, a manual git pull within each submodule will be required.

4.6 Remove Submodule

git submodule deinit <submodule> # Update .git/config.
git rm <submodule> # Remove submodule files.