maint: document dislike of mismatched if/else bracing

* docs/hacking.html.in (Curly braces): Tighten recommendations to
disallow if (cond) one-line; else { block; }.
* HACKING: Regenerate.
Suggested by Daniel P. Berrange.

HACKING

@@ -161,33 +161,42 @@ Do this, instead:
 
 However, there is one exception in the other direction, when even a one-line
 block should have braces. That occurs when that one-line, brace-less block is
-an "else" block, and the corresponding "then" block *does* use braces. In that
-case, either put braces around the "else" block, or negate the "if"-condition
-and swap the bodies, putting the one-line block first and making the longer,
-multi-line block be the "else" block.
+an "if" or "else" block, and the counterpart block *does* use braces. In that
+case, put braces around both blocks. Also, if the "else" block is much shorter
+than the "if" block, consider negating the "if"-condition and swapping the
+bodies, putting the short block first and making the longer, multi-line block
+be the "else" block.
 
   if (expr) {
       ...
       ...
   }
   else
-      x = y;    // BAD: braceless "else" with braced "then"
+      x = y;    // BAD: braceless "else" with braced "then",
+                // and short block last
 
-This is preferred, especially when the multi-line body is more than a few
-lines long, because it is easier to read and grasp the semantics of an
-if-then-else block when the simpler block occurs first, rather than after the
-more involved block:
-
-  if (!expr)
-    x = y; // putting the smaller block first is more readable
+  if (expr)
+      x = y;    // BAD: braceless "if" with braced "else"
   else {
       ...
       ...
   }
 
-If you'd rather not negate the condition, then at least add braces:
+Keeping braces consistent and putting the short block first is preferred,
+especially when the multi-line body is more than a few lines long, because it
+is easier to read and grasp the semantics of an if-then-else block when the
+simpler block occurs first, rather than after the more involved block:
 
-  if (expr) {
+  if (!expr) {
+    x = y; // putting the smaller block first is more readable
+  } else {
+      ...
+      ...
+  }
+
+But if negating a complex condition is too ugly, then at least add braces:
+
+  if (complex expr not worth negating) {
       ...
       ...
   } else {