Reading the Graph: git log --graph --oneline

Learning Objectives

By the end of this lesson you will be able to:

• Read the ASCII graph Git draws and identify branches and merges in it
• Build a log command that shows dates, authors and branch labels usefully
• Find which merge brought a given commit into main
• Use the graph to answer "what is in this build?" precisely

The Command Worth Aliasing

git log --graph --oneline --decorate --all

Four flags, and each one earns its place:

That last one matters more than it looks. Without --all you only see the ancestry of your current branch, which quietly hides everything you were probably trying to look at.

Because you will type this constantly, alias it once:

git config --global alias.lg "log --graph --oneline --decorate --all"

Then it is just git lg.

Reading the Shape

*   9a1b2c3 (HEAD -> main) Merge branch 'feature/auth-test'
|\
| * d4e5f6a (feature/auth-test) Add negative cases for expired token
| * c3d4e5f Add auth test fixtures
* | b2c3d4e Fix session timeout calculation
* | a1b2c3d Update dependency versions
|/
* 8f3c2a1 (tag: v2.4.0) Add password reset endpoint

Read it bottom-up — that is chronological order.

• 8f3c2a1 is where the two lines split. It carries the tag v2.4.0.
• The left column continued as main: two commits, a1b2c3d and b2c3d4e.
• The right column is feature/auth-test: two commits, c3d4e5f and d4e5f6a.
• |\ at the top marks a commit with two parents — the merge commit.
• 9a1b2c3 is that merge, and HEAD -> main says it is where you are standing.

Once you can see that shape, you can answer "what did this merge bring in?" by reading the right-hand column.

Useful Variations

git log --graph --oneline --merges

Only the merge commits. On a --no-ff team, this is a list of every feature that has landed — the most compact release summary available.

git log --graph --pretty=format:"%h %ad %an %s" --date=short --all

Adds the date and author to each line, which is what you want when you are building a timeline of when something broke.

git log --graph --oneline v2.4.0..HEAD

Everything since the last release tag. When someone asks "what's in this build?", this is the answer — and it comes with the branch structure attached.

git log --oneline --graph --first-parent main

Follows only the first parent of each merge, which on main means "one line per feature that landed" rather than every individual commit inside them. A very good high-level view.

Finding Where a Commit Landed

You have a commit ID from a bug report and want to know which merge brought it into main:

git log --merges --oneline --ancestry-path d4e5f6a..main

The last line of that output is the merge commit that first carried d4e5f6a into main. From there, git show <merge-id> tells you the branch name and everything else that arrived with it.

Also useful, and much simpler:

git branch --contains d4e5f6a
git tag --contains d4e5f6a

"Which branches have this commit?" and "which releases shipped it?" — two questions QA asks constantly, answered directly.

Pro Tip: Graphical clients (GitKraken, the history view in your IDE, the Network graph on GitHub) draw the same information with colours and curves. Use them. The ASCII version is what is always available, on any machine, over SSH, with no setup — which is why it is worth being able to read.

Key Takeaways

• git log --graph --oneline --decorate --all is the everyday graph command; alias it
• Read the graph bottom-up; |\ marks a merge commit's two parents
• --decorate labels which commits the branches and tags point at
• --merges alone gives a compact list of everything that has landed
• v2.4.0..HEAD scopes the log to a single build or release
• git branch --contains and git tag --contains answer "where did this commit end up?"