Git & the working environment

A history of your experiments

The supplied Git introduction introduces version control, terminal commands, editors, remote repositories and branching. A repository records snapshots of a project so an implementation can be compared with an earlier version. This is especially useful when experimenting with an algorithm: keep a correct baseline before changing its logic.

A working tree is the set of files you edit. The staging area selects the changes for the next snapshot. A commit stores that snapshot with a message. Saving a file in an editor does not create a commit.

The local Git workflow

Inspect your changes before staging them. Commit a coherent change with a message explaining its purpose. The following is a supplementary example of the workflow introduced in the slides.

• git status reports staged, unstaged and untracked files.
• git diff compares edits with the index; git diff --staged reviews the next commit.
• git log shows committed history. A commit is local until it is pushed.

1git status2git diff3git add Euclid.java4git commit -m "Add Euclidean algorithm example"

Branches and remote repositories

A branch is a movable name for a line of commits. The slides use git branch login and git checkout login to create and switch to a branch. Keep the original implementation and explore an alternative on a new branch.

A remote such as GitHub stores another copy of the repository. Clone creates a local copy. Fetch downloads remote history; merge integrates another line of development. A merge conflict requires you to inspect both changes and select the intended result.

• The slides use the branch name master. Use the branch name that actually exists in your repository.
• Configure your own name and email for commits. Do not copy somebody else’s identity.
• A .gitignore file excludes matching untracked artifacts; it does not remove files already tracked.

1git branch experiment2git checkout experiment3# Make and commit an isolated experiment4git checkout main5git merge experiment

Files, directories and editors

The slides introduce cd for changing directories, mkdir for creating a directory, and ls on Unix-like systems or dir in Windows Command Prompt for listing files. Relative paths begin at the current directory; .. refers to its parent.

Choose a text editor that preserves plain source text. Compile and run from the directory containing the intended Java files. Keep generated class files and editor metadata separate from academic source files.

Remember for revision

Working tree → staging area → commit is the core local sequence. A branch lets you compare experiments. A remote supports sharing and backup. Always inspect the changes you intend to commit.

Check your understanding

Supplementary practice. Try each question before opening the answer.