How can I see the changes in a Git commit?

Question

When I do git diff COMMIT I see the changes between that commit and HEAD (as far as I know), but I would like to see the changes that were made by that single commit.

I haven't found any obvious options on diff / log that will give me that output.

Answer 1

To see the diff for a particular COMMIT hash, where COMMIT is the hash of the commit:

git diff COMMIT~ COMMIT will show you the difference between that COMMIT's ancestor and the COMMIT. See the man pages for git diff for details about the command and gitrevisions about the ~ notation and its friends.

Alternatively, git show COMMIT will do something very similar. (The commit's data, including its diff - but not for merge commits.) See the git show manpage.

(also git diff COMMIT will show you the difference between that COMMIT and the head.)

Answer 2

As mentioned in "Shorthand for diff of git commit with its parent?", you can also use git diff with:

git diff COMMIT^! 

or

git diff-tree -p COMMIT 

With git show, you would need (in order to focus on diff alone) to do:

git show --color --pretty=format:%b COMMIT 

The COMMIT parameter is a commit-ish:

A commit object or an object that can be recursively dereferenced to a commit object. The following are all commit-ishes: a commit object, a tag object that points to a commit object, a tag object that points to a tag object that points to a commit object, etc.

See gitrevision "SPECIFYING REVISIONS" to reference a commit-ish.
See also "What does tree-ish mean in Git?".