diff --git a/diff.c b/diff.c
index 108c187577..cd3c8a3978 100644
--- a/diff.c
+++ b/diff.c
@@ -40,6 +40,7 @@
 #include "setup.h"
 #include "strmap.h"
 #include "ws.h"
+#include "write-or-die.h"
 
 #ifdef NO_FAST_WORKING_DIRECTORY
 #define FAST_WORKING_DIRECTORY 0
@@ -4404,8 +4405,33 @@ static void run_external_diff(const char *pgm,
 	diff_free_filespec_data(one);
 	diff_free_filespec_data(two);
 	cmd.use_shell = 1;
-	if (run_command(&cmd))
-		die(_("external diff died, stopping at %s"), name);
+	if (o->flags.diff_from_contents) {
+		int got_output = 0;
+		cmd.out = -1;
+		if (start_command(&cmd))
+			die(_("external diff died, stopping at %s"), name);
+		for (;;) {
+			char buffer[8192];
+			ssize_t len = xread(cmd.out, buffer, sizeof(buffer));
+			if (!len)
+				break;
+			if (len < 0)
+				die(_("unable to read from external diff,"
+				      " stopping at %s"), name);
+			got_output = 1;
+			if (write_in_full(1, buffer, len) < 0)
+				die(_("unable to write output of external diff,"
+				      " stopping at %s"), name);
+		}
+		close(cmd.out);
+		if (finish_command(&cmd))
+			die(_("external diff died, stopping at %s"), name);
+		if (got_output)
+			o->found_changes = 1;
+	} else {
+		if (run_command(&cmd))
+			die(_("external diff died, stopping at %s"), name);
+	}
 
 	remove_tempfile();
 }
@@ -4555,6 +4581,7 @@ static void run_diff_cmd(const char *pgm,
 			     o, complete_rewrite);
 	} else {
 		fprintf(o->file, "* Unmerged path %s\n", name);
+		o->found_changes = 1;
 	}
 }
 
@@ -4851,6 +4878,7 @@ void diff_setup_done(struct diff_options *options)
 	 */
 
 	if ((options->xdl_opts & XDF_WHITESPACE_FLAGS) ||
+	    options->flags.exit_with_status ||
 	    options->ignore_regex_nr)
 		options->flags.diff_from_contents = 1;
 	else
@@ -6741,7 +6769,7 @@ void diff_flush(struct diff_options *options)
 	if (output_format & DIFF_FORMAT_CALLBACK)
 		options->format_callback(q, options, options->format_callback_data);
 
-	if (output_format & DIFF_FORMAT_NO_OUTPUT &&
+	if ((!output_format || output_format & DIFF_FORMAT_NO_OUTPUT) &&
 	    options->flags.exit_with_status &&
 	    options->flags.diff_from_contents) {
 		/*
diff --git a/t/t4020-diff-external.sh b/t/t4020-diff-external.sh
index fdd865f7c3..26430ca66b 100755
--- a/t/t4020-diff-external.sh
+++ b/t/t4020-diff-external.sh
@@ -172,6 +172,14 @@ test_expect_success 'no diff with -diff' '
 	grep Binary out
 '
 
+test_expect_success 'diff.external and --exit-code with output' '
+	test_expect_code 1 git -c diff.external=echo diff --exit-code
+'
+
+test_expect_success 'diff.external and --exit-code without output' '
+	git -c diff.external=true diff --exit-code
+'
+
 echo NULZbetweenZwords | perl -pe 'y/Z/\000/' > file
 
 test_expect_success 'force diff with "diff"' '
diff --git a/t/t4046-diff-unmerged.sh b/t/t4046-diff-unmerged.sh
index fb8c51746e..afda629c98 100755
--- a/t/t4046-diff-unmerged.sh
+++ b/t/t4046-diff-unmerged.sh
@@ -98,4 +98,12 @@ test_expect_success 'diff --stat' '
 	test_cmp diff-stat.expect diff-stat.actual
 '
 
+test_expect_success 'diff --quiet' '
+	test_expect_code 1 git diff --cached --quiet
+'
+
+test_expect_success 'diff --quiet --ignore-all-space' '
+	test_expect_code 1 git diff --cached --quiet --ignore-all-space
+'
+
 test_done