Git and the command line: 50 essentials

All 50 cards

1. 1
   Start a new repository in the current folder
   bash

   git init

2. 2
   Stage changes hunk by hunk
   bash

   git add -p

3. 3
   Fix the last commit’s message or contents
   bash

   git commit --amend

   This rewrites the commit; avoid it on commits you’ve already pushed and shared.
4. 4
   Compact history graph
   bash

   git log --oneline --graph --all

5. 5
   git diff vs git diff --staged
   git diff shows unstaged changes; --staged shows what will go into the next commit
6. 6
   Create a branch and switch to it
   bash

   git switch -c feature/login

7. 7
   What does git merge do?
   Combines another branch into the current one, with a merge commit unless it can fast-forward
8. 8
   What does git rebase main do?
   Replays your branch’s commits on top of main, giving a linear history
9. 9
   Merge vs rebase
   Merge keeps history as it happened; rebase rewrites it to be linear. Don’t rebase commits others already have
10. 10
    Fast-forward merge
    When the target hasn’t diverged, Git just moves the branch pointer forward; no merge commit
11. 11
    Set work aside and get it back
    bash

    git stash
    git stash pop

12. 12
    git reset --soft HEAD~1
    Undo the last commit, keeping its changes staged
13. 13
    git reset HEAD~1 (mixed, the default)
    Undo the last commit, keeping its changes in the working tree, unstaged
14. 14
    git reset --hard HEAD~1
    Undo the last commit and discard its changes entirely

    Destructive. git reflog can still find the commit for a while.
15. 15
    Undo a pushed commit safely
    bash

    git revert <commit>

    Creates a new commit that reverses it, without rewriting history.
16. 16
    Find a commit you “lost” after a reset or rebase
    bash

    git reflog

    The reflog records every position HEAD has been at.
17. 17
    Apply one commit from another branch
    bash

    git cherry-pick <commit>

18. 18
    git fetch vs git pull
    fetch downloads remote changes; pull fetches and then merges (or rebases) them
19. 19
    Push a new branch and track it
    bash

    git push -u origin feature/login

20. 20
    Safer force push
    bash

    git push --force-with-lease

    Refuses if the remote moved since your last fetch, so you don’t overwrite others’ work.
21. 21
    What is .gitignore for?
    Patterns of untracked files Git should ignore, like build output and secrets
22. 22
    Discard local changes to a file
    bash

    git restore notes.md

23. 23
    Unstage a file but keep its changes
    bash

    git restore --staged notes.md

24. 24
    Detached HEAD
    HEAD points directly at a commit instead of a branch; new commits are easy to lose unless you create a branch
25. 25
    Find the commit that introduced a bug
    bash

    git bisect start
    git bisect bad
    git bisect good v1.0

    Git binary-searches history while you mark commits good or bad.
26. 26
    Create an annotated tag
    bash

    git tag -a v1.0 -m "First release"

27. 27
    Who last changed each line of a file?
    bash

    git blame app.ts

28. 28
    List remotes with their URLs
    bash

    git remote -v

29. 29
    HEAD~1 vs HEAD^2
    HEAD~1 is the first parent; HEAD^2 is the second parent of a merge commit
30. 30
    Show files changed in the last commit
    bash

    git show --stat

31. 31
    Print the current directory
    bash

    pwd

32. 32
    List all files, including hidden ones, with details
    bash

    ls -la

33. 33
    Go back to the previous directory
    bash

    cd -

34. 34
    Search files recursively, with line numbers
    bash

    grep -rn "TODO" src/

35. 35
    Find .log files modified more than 7 days ago
    bash

    find . -name "*.log" -mtime +7

36. 36
    What does a pipe | do?
    Sends one command’s standard output into the next command’s standard input
37. 37
    > vs >>
    > overwrites the file; >> appends to it
38. 38
    Send errors to the same place as output
    bash

    command > out.log 2>&1

39. 39
    Make a script executable
    bash

    chmod +x deploy.sh

40. 40
    What does chmod 755 mean?
    Owner can read, write and execute; group and others can read and execute
41. 41
    What does chmod 644 mean?
    Owner can read and write; group and others can only read
42. 42
    Find running node processes
    bash

    ps aux | grep node

43. 43
    kill vs kill -9
    kill sends SIGTERM (asks the process to exit); kill -9 sends SIGKILL, which can’t be caught
44. 44
    Delete files found by find
    bash

    find . -name "*.tmp" -print0 | xargs -0 rm

    -print0/-0 handle file names with spaces.
45. 45
    Show the exit status of the last command
    bash

    echo $?

    0 means success.
46. 46
    && vs || between commands
    a && b runs b only if a succeeded; a || b runs b only if a failed
47. 47
    Follow a log file as it grows
    bash

    tail -f app.log

48. 48
    Count lines in a file
    bash

    wc -l data.csv

49. 49
    Count how often each line occurs
    bash

    sort access.log | uniq -c | sort -rn

    uniq only merges adjacent lines, so sort first.
50. 50
    Generate an SSH key
    bash

    ssh-keygen -t ed25519 -C "[email protected]"