CIS241

System-Level Programming and Utilities

git (local)

Erik Fredericks, frederer@gvsu.edu
Fall 2025

Based on material provided by Erin Carrier, Austin Ferguson, and Katherine Bowers

Local!

git: repositories

Git repositories contain:

• A set of commit objects, and
• A set of references to commit objects (heads)

Git repositories are stored:

• In a .git sub-directory in the same directory as the project
• There is no central repository server

Git is distributed!

git: commit objects

Commit objects contain:

• A set of files (one version each),
• References to parent commit objects, and
• An SHA1 identifier that uniquely* identifies the commit

If two commits are exactly the same, the identifier will be the same.

git : commit objects

Common references

• HEAD: reference to tip of current branch
• index: staging area
• SHA-1 hashes: commit references

Common local operations

• git init : create new repository
• git add : stage changes to file (or add untracked file)
• git rm : remove (add -rf to recursively remove a directory)
• git mv : rename/move
• git commit : commit staged changes

git : commit objects

well then

How do you access commit objects if you don’t know their identifier?

Common local operations

• git status : view ... status
• git diff : view changes/differences
• git log : view list of commits
• git show <sha1> : view info about a particular commit

NOTE

• Running git checkout <sha1> will leave you in a DETACHED HEAD state!
  • Run git checkout main to get back to your normal tree
  • Unless if you were branching...
    • https://stackoverflow.com/questions/7539130/go-to-a-particular-revision

Common fixes to mistakes!

• Local mistakes

Common fixes to mistakes

I added (staged) a file but didn't mean to

• Meaning, when you commit/push it will be tracked forever

Options:

• git restore --staged filename (the new way)
• git reset filename (old way)

Common fixes to mistakes

I've really screwed up a file, I just want to get rid of all my changes

Options:

• git restore filename (the new way)
• git checkout filename (the old way)
  • git checkout -- filename (if branch exists with same name as file)

However, if already staged (meaning you did git add):

• git restore --staged --worktree filename

Common fixes to mistakes

Now you've done it - you messed up your local working directory! How do I go back

• git reset --hard
  • CAREFUL -- THIS DELETES THINGS
• git restore --staged --worktree . (from top level directory in repo)

One more helpful thing

Get yourself a visual diff editor

• Muuuuch easier than using diff
• DiffMerge, BeyondCompare, Meld, WinMerge...

Command cheatsheet

Main file manipulation git commands:

• git init - Initialize git repo in folder
• git add file - Add files/changes to staging area (truck)
• git mv source dest - Move/rename file and stage
• git rm file - Delete file and stage
• git commit -m "message" - Commit staged changes to local repo

Status commands

• git status - View which files changed since last commit
• git diff file - View how file changed since last commit
• git diff - View how all files changed
• git log - View list of commits