pickaxe: die when -G and --pickaxe-regex are combined

When the -G and --pickaxe-regex options are combined we simply ignore
the --pickaxe-regex option. Let's die instead as suggested by our
documentation, since -G is always a regex.

When --pickaxe-regex was added in d01d8c6782 (Support for pickaxe
matching regular expressions, 2006-03-29) only the -S option
existed. Then when -G was added in f506b8e8b5 (git log/diff: add
-G<regexp> that greps in the patch text, 2010-08-23) neither the
documentation for --pickaxe-regex was updated accordingly, nor was
something like this assertion added.

Since 5bc3f0b567 (diffcore-pickaxe doc: document -S and -G properly,
2013-05-31) we've claimed that --pickaxe-regex should only be used
with -S, but have silently tolerated combining it with -G, let's die
instead.

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

diff.c

@@ -4628,6 +4628,9 @@ void diff_setup_done(struct diff_options *options)
 	if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_MASK))
 		die(_("-G, -S and --find-object are mutually exclusive"));
 
+	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"));
+
 	/*
 	 * Most of the time we can say "there are changes"
 	 * only by checking if there are changed paths, but

diff.h

@@ -556,6 +556,8 @@ int git_config_rename(const char *var, const char *value);
 #define DIFF_PICKAXE_KINDS_MASK (DIFF_PICKAXE_KIND_S | \
 				 DIFF_PICKAXE_KIND_G | \
 				 DIFF_PICKAXE_KIND_OBJFIND)
+#define DIFF_PICKAXE_KINDS_G_REGEX_MASK (DIFF_PICKAXE_KIND_G | \
+					 DIFF_PICKAXE_REGEX)
 
 #define DIFF_PICKAXE_IGNORE_CASE	32
 

t/t4209-log-pickaxe.sh

@@ -66,6 +66,11 @@ test_expect_success 'usage' '
 	grep "mutually exclusive" err
 '
 
+test_expect_success 'usage: --pickaxe-regex' '
+	test_expect_code 128 git log -Gregex --pickaxe-regex 2>err &&
+	grep "mutually exclusive" err
+'
+
 test_expect_success 'usage: --no-pickaxe-regex' '
 	cat >expect <<-\EOF &&
 	fatal: unrecognized argument: --no-pickaxe-regex