show-branch: reject --[no-](topo|date)-order

"git show-branch --no-topo-order" behaved exactly the same way as
"git show-branch --topo-order" did, which was nonsense.  This was
because we choose between topo- and date- by setting a variable to
either REV_SORT_IN_GRAPH_ORDER or REV_SORT_BY_COMMIT_DATE with
OPT_SET_INT() and REV_SORT_IN_GRAPH_ORDER happens to be 0.  The
OPT_SET_INT() macro assigns 0 to the target variable in respose to
the negated form of its option.

"--no-date-order" by luck behaves identically to "--topo-order"
exactly for the same reason, and it sort-of makes sense right now,
but the "sort-of makes sense" will quickly break down once we add a
third way to sort.  Not-A may be B when there are only two choices
between A and B, but once your choices become among A, B, and C,
not-A does not mean B.

Just mark these two ordering options to reject negation, and add a
test, which was missing.  "git show-branch --no-reflog" is also
unnegatable, so throw in a test for that while we are at it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/show-branch.c

@@ -667,17 +667,17 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 			 N_("show possible merge bases")),
 		OPT_BOOL(0, "independent", &independent,
 			    N_("show refs unreachable from any other ref")),
-		OPT_SET_INT(0, "topo-order", &sort_order,
-			    N_("show commits in topological order"),
-			    REV_SORT_IN_GRAPH_ORDER),
+		OPT_SET_INT_F(0, "topo-order", &sort_order,
+			      N_("show commits in topological order"),
+			      REV_SORT_IN_GRAPH_ORDER, PARSE_OPT_NONEG),
 		OPT_BOOL(0, "topics", &topics,
 			 N_("show only commits not on the first branch")),
 		OPT_SET_INT(0, "sparse", &sparse,
 			    N_("show merges reachable from only one tip"), 1),
-		OPT_SET_INT(0, "date-order", &sort_order,
-			    N_("topologically sort, maintaining date order "
-			       "where possible"),
-			    REV_SORT_BY_COMMIT_DATE),
+		OPT_SET_INT_F(0, "date-order", &sort_order,
+			      N_("topologically sort, maintaining date order "
+				 "where possible"),
+			      REV_SORT_BY_COMMIT_DATE, PARSE_OPT_NONEG),
 		OPT_CALLBACK_F('g', "reflog", &reflog_base, N_("<n>[,<base>]"),
 			    N_("show <n> most recent ref-log entries starting at "
 			       "base"),

t/t3202-show-branch.sh

@@ -213,6 +213,15 @@ done <<\EOF
 --reflog --current
 EOF
 
+# unnegatable options
+for opt in topo-order date-order reflog
+do
+	test_expect_success "show-branch --no-$opt (should fail)" '
+		test_must_fail git show-branch --no-$opt 2>err &&
+		grep "unknown option .no-$opt." err
+	'
+done
+
 test_expect_success 'error descriptions on non-existent branch' '
 	cat >expect <<-EOF &&
 	error: No branch named '\''non-existent'\'.'