Setting Up Your Identity

Before making any commits, configure your username and email. This step is mandatory once per Git installation; lacking it will cause commit failures.

git config --global user.name "your name"
git config --global user.email "your@email.com"

Starting a Local Repository

Navigate to your project folder and initialize version control:

git init

This creates a hidden .git directory holding the repository metadata. On Linux/macOS, use ll -a to see it; on Windows you can enable hidden items view.

Checking Repository Status

To see untracked and modified files at any time:

git status

After creating a file such as notes.txt, running the status command shows it as untracked (red).

Staging Files

Move a file to the staging area before committing:

git add notes.txt

A warning about line endings may appear – Git automatically converts them. Run git status again; the file will now appear in green, ready to be committed.

Committing to the Local Repository

Record the staged snapshot with a descriptive message:

git commit -m "add initial notes"

Subsequent git status output will confirm a clean working tree.

Viewing History

For a compact log with shortened commit hashes:

git reflog

For the full commit history:

git log

Modifying Files and Tracking Changes

Edit the same file and run git status to see it listed as modified. Stage it again:

git add notes.txt
git commit -m "update content"

Now the log shows multiple commit entries.

Traversing Versions

To move the HEAD and working directory to any previous commit, use the hard reset with the commit hash from reflog:

git reset --hard <commit-hash>

Branching Essentials

Branches let you isolate work without affecting the main line, and they facilitate parallel development.

Listing Branches

git branch -v

Creating a New Branch

git branch feature-login

Switching Branches

git checkout feature-login

While on the new branch, any file modifications remain local to that branch. Switching back to master will reveal the previous state of the code.

Merging Branches

To integrate a branch into the current one:

git merge feature-login

A conflict arises when the same parts of a file were changed on both branches. Suppose master changes the last line, and feature-login changes the second-to-last line. Merging produces a conflict. You must manually resolve it by editing the file, removing conflict markers (<<<<<<<, =======, >>>>>>>), and keeping the desired version. After saving:

git add .
git commit -m "resolve merge conflict"

The merge applies only to the current branch; the source branch remains untouched.

Collaboration Models

Within a team: colleagues clone the same repository, push to and pull from a shared remote, and often work on feature branches.

Cross-team collaboration: one team forks the original repo, makes changes, and submits a pull request to the upstream project.

IntelliJ IDEA Integration with Git

Preparing Ignore Rules

Create a .gitignore file in your user home (or the .gitconfig location) to exclude IDE artifacts and build outputs:

*.class
*.log
.idea/
target/
*.iml
*.jar
*.war
.classpath
.project
.settings

Configuring Git in IDE

In IDEA, set the path to the Git executable under Settings | Version Control | Git. Create a new Maven module, delete any existing .gitignore if present, then go to VCS | Enable Version Control Integration and choose Git. The project files will appear red (unversioned).

Committing and Pushing

Select the project, click Git | Add to stage, then Git | Commit Directory. After providing a message, commit. The first commit will turn the files to normal color. Subsequent changes appear in blue or green.

Switching Versions

After multiple commits, open the Git tool window. The yellow tag marks the HEAD, the green labels indiccate branches. Right-click on any commit and choose Checkout Revision to jump to that version.

Branch Operations via IDE

Right-click the project and select Git | Branches | New Branch to create a branch. To switch, use the branches popup in the bottom-right corner. Merging follows the same conceptual steps: while on master, choose Git | Branches | Merge and select the source branch. If conflicts occur, IDEA displays a dialog with a merge tool; you can accept one side or manually edit the result, then apply and commit.

Connecting to Gitee

Creating a Remote Repository

On Gitee, create a new repository. Avoid initializing it with a README if you intend to push an existing project, as it may cause push conflicts.

Installing the Plugin

In IDEA, go to Settings | Plugins, search for Gitee, install and restart. Then log in to your Gitee account through Settings | Version Control | Gitee.

Pushing to Remote

With a local repository ready, use VCS | Git | Push (or Ctrl+Shift+K). Set the remote URL to your Gitee repository and push the current branch.

Pulling Changes from Gitee

If someone modifies files directly on Gitee, return to IDEA and use VCS | Git | Pull to fetch and merge those updates into your local working branch.