A developer is working on a branch called topic that was created from the master branch to add a new feature to the product. After making a few commits on the branch, the developer wants to compare…

git diff topic --cached compares the topic branch against the staging area (index), not against the master branch.

git diff topic...master uses three-dot notation, which shows only changes introduced on master since the common ancestor with topic - not a direct tip-to-tip branch comparison.

git diff topic HEAD compares the tip of the topic branch against HEAD, which resolves to the latest commit on the currently checked-out branch. When the user is on master, HEAD equals the master tip, making this functionally identical to a direct branch comparison. It reveals all file-level differences between topic and master without typing the branch name explicitly.

git diff topic-master treats 'topic-master' as a single branch or ref name rather than comparing two separate branches, which would result in an error unless that exact ref exists.

git diff topic master directly compares the latest commits of the topic and master branches by specifying both names as arguments. This is the most explicit and readable form of the command for comparing two named branches. It produces a complete diff of all changes present in one branch but not the other.