Pro Git Ch1 — Getting Started

  • Description: Notes on Pro Git (2nd ed.) Chapter 1 — version control concepts, Git's design (snapshot model, three states), installing Git, first-time setup, and the built-in help system.
  • My Notion Note ID: K2B-2-1
  • Created: 2020-06-02
  • Updated: 2026-05-19
  • License: Reuse is very welcome. Please credit Yu Zhang and link back to the original on yuzhang.io

Table of Contents

1. About Version Control

  • VCS = system that records changes to a file (or set of files) over time so you can recall specific versions later.
  • Three families, in order of increasing capability:
    • Local VCS — single-machine version database (e.g. RCS). Fragile if the machine dies.
    • Centralized VCS (CVCS) — single server holds history; clients check out latest snapshot (SVN, CVS, Perforce). Single point of failure.
    • Distributed VCS (DVCS) — every clone is a full backup with history (Git, Mercurial, Bazaar). Server is a convention, not a requirement.

2. A Short History of Git

  • Linux kernel used BitKeeper (proprietary DVCS) from 2002 to 2005.
  • 2005: BitKeeper free-use terms revoked → kernel community needed an alternative.
  • Linus Torvalds wrote Git in ~10 days. Design goals:
    • Speed.
    • Simple design.
    • Strong support for non-linear development (thousands of parallel branches).
    • Fully distributed.
    • Handle large projects (kernel-scale) efficiently.

3. What is Git

3.1 Snapshots, not differences

  • Each commit stores a reference to a snapshot of the entire tree at that point.
  • Unchanged files = pointer to the previous identical blob (no duplication).
  • This is fundamentally different from delta-based systems (SVN, CVS) that store per-file change history.

3.2 Nearly every operation is local

  • Full history lives in .git/ on your machine.
  • log, diff, commit, branch, merge all work offline.
  • Network only needed for fetch, pull, push, clone.

3.3 Integrity via SHA-1

  • Every object is content-addressed by a 40-hex-character SHA-1 hash.
  • Cannot change a file or commit without Git knowing — the hash changes.
  • (Git is migrating toward SHA-256 as an opt-in object format; SHA-1 is still the default.)

3.4 Only adds data

  • Once committed, data is hard to lose — recoverable via reflog and dangling objects for ~90 days (default).
  • The git rm/git reset --hard etc. don't delete history; they move pointers.

3.5 Three states / three areas

State Where Meaning
Modified Working tree Edited but not yet staged.
Staged Index (.git/index) Marked for inclusion in the next commit.
Committed Repo (.git/) Snapshot stored in the object database.

Basic workflow: edit → git add → git commit.

4. The Command Line

  • Pro Git assumes CLI — the only interface where all commands are available.
  • GUI tools (GitHub Desktop, Tower, SourceTree, GitKraken) implement a subset, often missing advanced operations.
  • macOS / Linux: built-in terminal. Windows: Git Bash (ships with Git for Windows) or PowerShell.

5. Installing Git

# Linux
sudo apt install git-all              # Debian/Ubuntu
sudo dnf install git-all              # Fedora/RHEL

# macOS
brew install git                       # Homebrew
git --version                          # triggers Xcode CLI tools install on first run

# Windows
# Download installer from https://git-scm.com (includes Git Bash)

# Verify
git --version

Building from source gives the most up-to-date version; needs gcc, openssl, curl, expat, gettext, zlib.

6. First-Time Setup

6.1 Config scopes

Three levels, lowest wins on read:

File Flag Scope
/etc/gitconfig --system All users on this machine.
~/.gitconfig or ~/.config/git/config --global Current user.
<repo>/.git/config --local (default) Single repo.

6.2 Required identity

git config --global user.name "Yu Zhang"
git config --global user.email "[email protected]"

6.3 Common extras

git config --global core.editor vim
git config --global init.defaultBranch main      # Git 2.28+
git config --global pull.rebase true             # rebase on pull instead of merge
git config --global credential.helper cache      # short-term username/password cache

6.4 Inspect

git config --list                      # all sources merged
git config --list --show-origin        # which file each setting came from
git config user.name                   # single key

7. Getting Help

Three equivalent forms for the full manual:

git help <command>
git <command> --help
man git-<command>

Other:

  • git <command> -h — short usage summary.
  • git help <concept> — concept guides (e.g. git help everyday, git help workflows, git help glossary).
  • git help -g — list all installed guides.

8. References