diff --check: minor fixups

There is no reason --exit-code and --check-diff must be mutually
exclusive, so assign different bits to different results and allow them
to be returned from the command.  Introduce diff_result_code() to factor
out the common code to decide final status code based on diffopt
settings and use it everywhere.

Update tests to match the above fix.

Turning pager off when "diff --check" is used is a regression.

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

builtin-diff-files.c

@@ -31,9 +31,5 @@ int cmd_diff_files(int argc, const char **argv, const char *prefix)
 	if (!rev.diffopt.output_format)
 		rev.diffopt.output_format = DIFF_FORMAT_RAW;
 	result = run_diff_files_cmd(&rev, argc, argv);
-	if (DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
-		return DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0;
-	if (rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
-		return DIFF_OPT_TST(&rev.diffopt, CHECK_FAILED) != 0;
-	return result;
+	return diff_result_code(&rev.diffopt, result);
 }

builtin-diff-index.c

@@ -44,9 +44,5 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 		return -1;
 	}
 	result = run_diff_index(&rev, cached);
-	if (DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
-		return DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0;
-	if (rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
-		return DIFF_OPT_TST(&rev.diffopt, CHECK_FAILED) != 0;
-	return result;
+	return diff_result_code(&rev.diffopt, result);
 }

builtin-diff-tree.c

@@ -132,8 +132,6 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 				diff_tree_stdin(line);
 		}
 	}
-	if (opt->diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
-		return DIFF_OPT_TST(&opt->diffopt, CHECK_FAILED) != 0;
-	return DIFF_OPT_TST(&opt->diffopt, EXIT_WITH_STATUS)
-		&& DIFF_OPT_TST(&opt->diffopt, HAS_CHANGES);
+
+	return diff_result_code(&opt->diffopt, 0);
 }

builtin-diff.c

@@ -244,11 +244,11 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	DIFF_OPT_SET(&rev.diffopt, ALLOW_EXTERNAL);
 	DIFF_OPT_SET(&rev.diffopt, RECURSIVE);
 
-	/* If the user asked for our exit code then don't start a
+	/*
+	 * If the user asked for our exit code then don't start a
 	 * pager or we would end up reporting its exit code instead.
 	 */
-	if (!DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS) &&
-	    (!(rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)))
+	if (!DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
 		setup_pager();
 
 	/* Do we have --cached and not have a pending object, then
@@ -352,10 +352,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	else
 		result = builtin_diff_combined(&rev, argc, argv,
 					     ent, ents);
-	if (DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
-		result = DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0;
-	if (rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
-		return DIFF_OPT_TST(&rev.diffopt, CHECK_FAILED) != 0;
+	result = diff_result_code(&rev.diffopt, result);
 	if (1 < rev.diffopt.skip_stat_unmatch)
 		refresh_index_quietly();
 	return result;

diff.c

@@ -2125,12 +2125,7 @@ int diff_setup_done(struct diff_options *options)
 	if (options->output_format & DIFF_FORMAT_NAME_STATUS)
 		count++;
 	if (options->output_format & DIFF_FORMAT_CHECKDIFF)
-	{
 		count++;
-		if (DIFF_OPT_TST(options, QUIET) ||
-		    DIFF_OPT_TST(options, EXIT_WITH_STATUS))
-			die("--check may not be used with --quiet or --exit-code");
-	}
 	if (options->output_format & DIFF_FORMAT_NO_OUTPUT)
 		count++;
 	if (count > 1)
@@ -3180,6 +3175,20 @@ void diffcore_std(struct diff_options *options)
 		DIFF_OPT_CLR(options, HAS_CHANGES);
 }
 
+int diff_result_code(struct diff_options *opt, int status)
+{
+	int result = 0;
+	if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
+	    !(opt->output_format & DIFF_FORMAT_CHECKDIFF))
+		return status;
+	if (DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
+	    DIFF_OPT_TST(opt, HAS_CHANGES))
+		result |= 01;
+	if ((opt->output_format & DIFF_FORMAT_CHECKDIFF) &&
+	    DIFF_OPT_TST(opt, CHECK_FAILED))
+		result |= 02;
+	return result;
+}
 
 void diff_addremove(struct diff_options *options,
 		    int addremove, unsigned mode,

diff.h

@@ -247,4 +247,6 @@ extern int run_diff_index(struct rev_info *revs, int cached);
 extern int do_diff_cache(const unsigned char *, struct diff_options *);
 extern int diff_flush_patch_id(struct diff_options *, unsigned char *);
 
+extern int diff_result_code(struct diff_options *, int);
+
 #endif /* DIFF_H */

t/t4015-diff-whitespace.sh

@@ -148,14 +148,14 @@ test_expect_failure 'check with space before tab in indent' '
 
 '
 
-test_expect_failure '--check and --exit-code are exclusive' '
+test_expect_success '--check and --exit-code are not exclusive' '
 
 	git checkout x &&
 	git diff --check --exit-code
 
 '
 
-test_expect_failure '--check and --quiet are exclusive' '
+test_expect_success '--check and --quiet are not exclusive' '
 
 	git diff --check --quiet