tests: Add newlines with VIR_TEST_REGENERATE_OUTPUT

Since test files are formatted predictably nowadays, we can make
VIR_TEST_REGENERATE_OUTPUT handle most cases for us with a simple
replacement. test-wrap-argv.pl is still canon, but this bit makes
it easier to confirm test output changes during active development.

tests/testutils.c

@@ -469,10 +469,19 @@ virtTestDifferenceFullInternal(FILE *stream,
     actualStart = actual;
     actualEnd = actual + (strlen(actual)-1);
 
-    if (regenerate && virTestGetRegenerate() > 0) {
+    if (regenerate && (virTestGetRegenerate() > 0) && expectName && actual) {
+        char *regencontent;
+
+        /* Try to properly indent qemu argv files */
+        if (!(regencontent = virStringReplace(actual, " -", " \\\n-")))
+            return -1;
+
         if (expectName && actual &&
-            virFileWriteStr(expectName, actual, 0666) < 0)
+            virFileWriteStr(expectName, regencontent, 0666) < 0) {
+            VIR_FREE(regencontent);
             return -1;
+        }
+        VIR_FREE(regencontent);
     }
 
     if (!virTestGetDebug())