Deep dive into git
This is the demo repo for a hands-on lab for working with git from the command line.
Before you start
Check yor git installation
Make sure git is installed and the version is > 2.23:
$ git --version
> git version 2.35.1
If not, download and install git.
Check your git config
- Check your name and email address:
$ git config --global user.name
$ git config --global user.email
If this does not return the desired values, set the config using these commands:
$ git config --global user.name '<your_name>'
$ git config --global user.email '<your_email_address>'
- Set the default branch to
main:
$ git config --global init.defaultBranch main
- Check your default editor
Check your default editor (i.e. by running git config --global --edit). If you like the editor, then you are good. If your stuck in vim (click ESC : q ! Enter to exit), then configure the editor of your choice - for example CSCode:
$ git config --global core.editor 'code --wait'
Exercise 1: Understanding git
Set-up:
Create a local file/folder:
mkdir UnderstandingGit
cd UnderstandingGit
mkdir folder;
for d in {1..6}; do echo "Line ${d}" >> folder/file.txt; done;
Powershell:
mkdir UnderstandingGit
cd UnderstandingGit
mkdir folder
for ($d=1; $d -le 6; $d++) { "Line $d" >> folder\file.txt }
Exercise
- Modify the file and verify its SHA value (
git hash-object)
- Initialize the git repo (
git init) and check the changes in your folder.
- Add file to index (
git add).
- Commit file and check in your
.git folder what a commit is (git cat-file and git ls-tree).
- Add another commit and verify how the two commits are connected.
- Create a sinple tag and an annotated tag (
git tag and git tag -a).
Important commands for this exercise:
```
$ git hash-object folder/file.txt
$ git init
$ git add
$ git commit
$ git ls-tree
$ git cat-file [-p | -t]
$ cat
$ git tag [-a]
```
A commit is a tree of blobs and trees:
graph BT;
Tree==>Commit;
Blob==>Tree;
Blob2==>Tree;
Tree2==>Tree;
Blob3==>Tree2;
Blob4==>Tree2;
Tree3==>Tree2;
Blob5==>Tree3;
The commits are connected to their parent commits (DAG):
graph RL;
96a85==>49c01;
7e536==>96a85;
1e542==>7e536;
b7e6b==>1e542;
main-.->b7e6b;
HEAD-->main;
5a053==>7e536;
55805==>5a053;
branch-.->55805;
tag-.->55805;
Exercise 2: Working with patches:
- Check how git generates diffs (
git diff).
- Create patches for your two commits (
git format-patch).
- Undo your changes (
git reset).
- Apply the patches (
git apply and git am).
Important commands for this exercise:
```console
$ git diff
$ git format-patch HEAD~2..HEAD
$ git reset --hard HEAD~2
$ git apply
$ git am
```
Exercise 3: Merge conflicts
Set-up
echo "Solving merge conflicts in git is easy" > Merge.txt
git add Merge.txt
git commit -m "Base commit"
git switch -c experiment
echo "Solving merge conflicts is easy in git" > Merge.txt
git commit -am "Modify Merge.txt in experiment"
git switch main
echo "Solving merge conflicts in git is very easy" > Merge.txt
git commit -am "Modify Merge.txt in main"
git switch experiment
Exercise
Create a merge conflict with git merge main and resolve it.
Important commands for this exercise:
```console
$ git config --global merge.conflictStyle diff3
$ git merge --abort
$ git diff
$ git log --merge –p
$ git show :1: (common ancestor)
$ git show :2: (HEAD)
$ git show :3: (MERGE_HEAD)
$ git add
$ git merge --continue
```
</details>
## Exercise 4: Working with your local history
### Set-up:
Create a local history:
```console
mkdir WorkingWithYourHistory
cd WorkingWithYourHistory
git init
for d in {1..6}; do touch "file${d}.md"; git add "file${d}.md"; git commit -m "adding file ${d}"; done
```
Look at you history. Create a git alias so that you don't have to type the long command all the time.
```console
$ git log --oneline --graph --decorate --all
$ git config --global alias.lol 'log --oneline --graph --decorate --all'
```
### Exercise
1. Add another file (`File7.md`) and ammend it to te last commit.
2. Reset the last two commits and commit them together as a new commit (`git reset --soft`).
3. Reset the last commit and create three commits out of it (`git reset --mixed`).
4. Undo the last three commit (`git reset --hard`).
5. Cherry pick the changes from the reflog.
6. Do an interactive rebase. Reword commit 2 and edit commit 3.
Important commands for this exercise:
```console
$ git commit --amend
$ git reset [--hard | --soft | --mixed]
$ git reflog
$ git cherry-pick
$ git rebase [-i]
```
## Exercise 5: Branches, tags, finding bugs, and adding patches
### Set-up:
```console
$ git clone https://github.com/wulfland/DeepDive.git DeepDive
$ cd DeepDive
```
### Exercise
1. Create a branch `fix-bug` to fix the bug (`git switch -c`)
2. Switch to `main` and search in the history for the bug (`inde.html` instead of `index.html`) using `git bisect`.
3. Modify Readme.md and commit to `main`.
4. Switch to `fix-bug` and rename `inde.html` to `index.html`.
5. Rebase the branch onto main.
6. Create a branch `slow-down`.
7. Modify line 9 of index.html and change the background URL to images/texture.jpg.
8. Modify line 78 of index.html and change the timing for the game to speed it up or slow it down.
9. Move `texture.jpg` to a new folder `images`.
10. Create seperate commits for refactoring and logic changes (`git add -p`).
11. Squash the changes into `main`
Important commands for this exercise:
```console
$ git switch [-c]
$ git bisect start
$ git bisect good
$ git bisect bad
$ git bisect start
$ git bisect run ls index.html
$ git add -p
$ git merge [--squash | --rebase]
```
</details>