fail if tree is dirty

.gitignore

@@ -10,3 +10,6 @@
 
 # Output of the go coverage tool, specifically when used with LiteIDE
 *.out
+
+# IDE files
+/.idea

README.md

@@ -35,7 +35,7 @@ Flags:
       --compare-imports    Compare exported API differences of the imports in the repo.
   -h, --help               help for go-apidiff
       --print-compatible   Print compatible API changes
-      --repo-path string   Path to root of git repository to compare (default "/home/joe/projects/work/kubernetes-sigs/controller-runtime")
+      --repo-path string   Path to root of git repository to compare (default "/home/myuser/myproject")
 ```
 
 ## Example

pkg/diff/run.go

@@ -46,6 +46,13 @@ func Run(opts Options) (*Diff, error) {
 		return nil, fmt.Errorf("failed to get git worktree: %w", err)
 	}
 
+
+	if stat, err := wt.Status(); err != nil {
+		return nil, fmt.Errorf("failed to get git status: %w", err)
+	} else if !stat.IsClean() {
+		return nil, fmt.Errorf("cannot compare with dirty git tree")
+	}
+
 	origRef, err := repo.Head()
 	if err != nil {
 		return nil, fmt.Errorf("failed to get current HEAD reference: %w", err)