Q8 of 40 · Git

How do you view the commit history? How do you make it readable?

GitJuniorgitloghistoryaliasesdebugging

Short answer

Short answer: git log --oneline --graph --decorate --all gives a compact one-line-per-commit graph with branch labels. Use --author, --since, --grep, or -S 'term' to filter. git log --stat shows changed files per commit. Set up a git alias (git config --global alias.lg 'log --oneline --graph --decorate --all') to avoid retyping.

Detail

Filtering history — practical patterns for QA engineers:

# Find the commit that changed a test file
git log --oneline -- tests/UserApiTest.java

# Search for commits that added or removed a string
git log -S "resetPassword" --oneline

# Commits by a specific author in the last 2 weeks
git log --author="Alice" --since="2 weeks ago" --oneline

# Commits that match a message pattern
git log --grep="fix:" --oneline

Graph view — essential in branchy repos: git log --oneline --graph --decorate --all shows the full branch tree in ASCII art. It's the fastest way to understand how branches relate and where merges happened.

git show <sha>: view the full diff of a single commit — useful for code-reviewing a specific change or understanding what a commit actually modified.

Setting up a permanent alias in ~/.gitconfig means you type git lg and get the full graph view without memorising flags.

// EXAMPLE

# Useful log alias — add to ~/.gitconfig
git config --global alias.lg   "log --color --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset' --abbrev-commit"
git lg

# Filter: all commits touching a specific test file
git log --oneline -- src/test/java/UserApiTest.java

# Search commit diffs for a string (the -S "pickaxe" flag)
git log -S "testGetUser" --oneline --all

# Show full diff of a single commit
git show a1b2c3d

# Compare two branches — commits in feature not in main
git log main..feature/login --oneline

// WHAT INTERVIEWERS LOOK FOR

Knowledge of --graph --decorate --all for branch visualisation, the -S pickaxe flag for searching diffs, and the main..branch notation for comparing branches. Engineers who know git log well debug regressions significantly faster.

// COMMON PITFALL

Using git log with no flags and reading through hundreds of full commit objects. --oneline makes history scannable; --graph makes branch structure visible. Both should be reflexive.

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