Add regex command implementation

tests/integration/regex_conflict_test.go

@@ -0,0 +1,26 @@
+package integration
+
+import (
+	"bytes"
+	"testing"
+
+	renamercmd "github.com/rogeecn/renamer/cmd"
+)
+
+func TestRegexApplyBlocksConflicts(t *testing.T) {
+	t.Parallel()
+
+	tmp := t.TempDir()
+	copyRegexFixtureIntegration(t, "case-fold", tmp)
+
+	cmd := renamercmd.NewRootCommand()
+	var out bytes.Buffer
+	cmd.SetOut(&out)
+	cmd.SetErr(&out)
+	cmd.SetArgs([]string{"regex", "^(.*)$", "conflict", "--yes", "--path", tmp})
+
+	err := cmd.Execute()
+	if err == nil {
+		t.Fatalf("expected error when conflicts are present")
+	}
+}