Comparing the Working Copy and Repository

Like in CVS and SVN, to see the changes in the working copy versus the current HEAD state of the repository, you use the diff command:

$ vi Main.groovy
$ git diff
diff --git a/src/Main.groovy b/src/Main.groovy
index 6191a10..29df7f5 100644
--- a/src/Main.groovy
+++ b/src/Main.groovy
@@ -3,12 +3,13 @@ import static Division.divide
 import static Subtract.subtract
 import static Sum.sum

-def name = "Matthew"
-int programmingPoints = 10
+def name = "Jeffrey"
+int programmingPoints = 20

 println "Hello ${name}"
 println "${name} has at least ${programmingPoints} programming points."
 println "${programmingPoints} squared is ${square(programmingPoints)}"
 println "${programmingPoints} divided by 2 bonus points is ${divide(programmingPoints, 2)}"
 println "${programmingPoints} minus 7 bonus points is ${subtract(programmingPoints, 7)}"
-println "${programmingPoints} plus 3 bonus points is ${sum(programmingPoints, 3)}"
\ No newline at end of file

You can also compare the state of the repository against a given commit (compare working copy against repository at the time of the given commit) or compare two different commits (compare the state of the repository at those two commits):

$ git diff ebbbf77 45a30ea
diff --git a/src/test/java/com/ambientideas/AppTest.java b/src/test/java/com/ambientideas/AppTest.java
new file mode 100644
index 0000000..c1ea083
--- /dev/null
+++ b/src/test/java/com/ambientideas/AppTest.java
@@ -0,0 +1,43 @@
+package com.ambientideas;
+
+import junit.framework.Test;
+import junit.framework.TestCase;
+import junit.framework.TestSuite;
+
+//Pending comments
...

Note that the diff output is relative to the order of the commit ids. If you reverse the commit ids, the diff output will similarly be reversed:

$ git diff 45a30ea ebbbf77
diff --git a/src/test/java/com/ambientideas/AppTest.java b/src/test/java/com/ambientideas/AppTest.java
deleted file mode 100644
index c1ea083..0000000
--- a/src/test/java/com/ambientideas/AppTest.java
+++ /dev/null
@@ -1,43 +0,0 @@
-package com.ambientideas;
-
-import junit.framework.Test;
-import junit.framework.TestCase;
-import junit.framework.TestSuite;
-
-//Pending comments