Viewing History

Explore your project's past with git log, git show and git diff

Your project’s diary

Every commit you make is stored forever (or until you deliberately remove it). In this module we’ll look at the three commands you use to explore that history:

• git log: the list of commits
• git show: what one commit changed
• git diff: what’s changed but isn’t committed yet

git log

Run this in your pico-bot folder:

git log

commit 8b1e4d07c2a9f35e1d6b0a4c7e8f9a2b3c4d5e6f (HEAD -> main)
Author: Ada Lovelace <[email protected]>
Date:   Wed Nov 4 10:42:13 2026 +0000

    Set up the left motor pin

commit 3f9c2a1b7d5e4f6a8c9b0d1e2f3a4b5c6d7e8f9a
Author: Ada Lovelace <[email protected]>
Date:   Wed Nov 4 10:31:02 2026 +0000

    Add start-up code that blinks the LED

The newest commit is at the top. Each one shows its full hash, the author, the date and the message. HEAD -> main marks where you are now: HEAD is Git’s name for “the commit you’ve currently got checked out”, and it’s on the main branch.

If there are lots of commits, Git shows them a page at a time. Press Space to see more, and q to quit.

A shorter log

Most of the time, you’ll want the one-line version:

git log --oneline

8b1e4d0 (HEAD -> main) Set up the left motor pin
3f9c2a1 Add start-up code that blinks the LED

You can use those short hashes anywhere Git asks for a commit.

Other handy options

git log --oneline -5          # only the last 5 commits
git log --oneline main.py     # only commits that changed main.py
git log --oneline --graph --all   # draw the branches as a graph

The --graph --all version becomes really useful once you start using branches in module 8.

git show

To see exactly what a commit changed, give git show its hash:

git show 8b1e4d0

commit 8b1e4d07c2a9f35e1d6b0a4c7e8f9a2b3c4d5e6f (HEAD -> main)
Author: Ada Lovelace <[email protected]>
Date:   Wed Nov 4 10:42:13 2026 +0000

    Set up the left motor pin

diff --git a/main.py b/main.py
index 1a2b3c4..5d6e7f8 100644
--- a/main.py
+++ b/main.py
@@ -3,6 +3,7 @@ from machine import Pin
 import time

 led = Pin("LED", Pin.OUT)
+left_motor = Pin(14, Pin.OUT)

 print("Pico-Bot starting up")

The bottom part is called a diff. Lines starting with + were added, lines starting with - were removed, and the others are shown for context. The @@ line tells you roughly where in the file the change is.

git show on its own (no hash) shows the latest commit.

git diff

git diff shows changes you haven’t committed yet. Add a right motor to main.py:

right_motor = Pin(15, Pin.OUT)

Then run:

git diff

diff --git a/main.py b/main.py
index 5d6e7f8..9a0b1c2 100644
--- a/main.py
+++ b/main.py
@@ -4,6 +4,7 @@ import time

 led = Pin("LED", Pin.OUT)
 left_motor = Pin(14, Pin.OUT)
+right_motor = Pin(15, Pin.OUT)

Here’s the catch: git diff compares your files with the staging area. Once you git add a change, plain git diff no longer shows it. To see what’s staged and about to be committed, use:

git diff --staged

So the full picture is:

A great habit: run git diff --staged just before every commit, and read through what you’re about to save.

Now commit the right motor:

git add main.py
git commit -m "Set up the right motor pin"

Try it yourself

1. Run git log --oneline and count your commits.
2. Use git show on your very first commit.
3. Make a change, run git diff, then git add it and run git diff again. Where did the change go? Find it with git diff --staged.
4. Challenge: run git log -p main.py. What does -p add?

Common issues

• Problem: The log fills the screen and you can’t type
• Solution: Press q to quit.

• Why: Git shows long output in a pager called less, which waits for you to scroll.

• Problem: git diff shows nothing, but you know you changed something
• Solution: Try git diff --staged.

• Why: Once a change is staged, plain git diff doesn’t show it.

• Problem: fatal: your current branch 'main' does not have any commits yet
• Solution: Make a commit first (module 4).
• Why: There’s no history to show until there’s at least one commit.

Check your understanding

You can use the arrows  ← → on your keyboard to navigate between lessons.