pickaxe: die when --find-object and --pickaxe-all are combined

Neither the --pickaxe-all documentation nor --find-object's has ever
suggested that you can combine the two. See f506b8e8b5 (git log/diff:
add -G<regexp> that greps in the patch text, 2010-08-23) and
15af58c1ad (diffcore: add a pickaxe option to find a specific blob,
2018-01-04).

But we've silently tolerated it, which makes the logic in
diffcore_pickaxe() harder to reason about. Let's assert that we won't
have the two combined.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -4631,6 +4631,9 @@ void diff_setup_done(struct diff_options *options)
 	if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_G_REGEX_MASK))
 		die(_("-G and --pickaxe-regex are mutually exclusive, use --pickaxe-regex with -S"));
 
+	if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_ALL_OBJFIND_MASK))
+		die(_("---pickaxe-all and --find-object are mutually exclusive, use --pickaxe-all with -G and -S"));
+
 	/*
 	 * Most of the time we can say "there are changes"
 	 * only by checking if there are changed paths, but

diff.h

@@ -558,6 +558,8 @@ int git_config_rename(const char *var, const char *value);
 				 DIFF_PICKAXE_KIND_OBJFIND)
 #define DIFF_PICKAXE_KINDS_G_REGEX_MASK (DIFF_PICKAXE_KIND_G | \
 					 DIFF_PICKAXE_REGEX)
+#define DIFF_PICKAXE_KINDS_ALL_OBJFIND_MASK (DIFF_PICKAXE_ALL | \
+					     DIFF_PICKAXE_KIND_OBJFIND)
 
 #define DIFF_PICKAXE_IGNORE_CASE	32
 

t/t4209-log-pickaxe.sh

@@ -63,6 +63,9 @@ test_expect_success 'usage' '
 	grep "mutually exclusive" err &&
 
 	test_expect_code 128 git log -Sstring --find-object=HEAD 2>err &&
+	grep "mutually exclusive" err &&
+
+	test_expect_code 128 git log --pickaxe-all --find-object=HEAD 2>err &&
 	grep "mutually exclusive" err
 '