Merge branch 'maint'

* maint:
  Teach "git diff" to honour --[no-]ext-diff

builtin-diff.c

@@ -290,6 +290,9 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	/* Otherwise, we are doing the usual "git" diff */
 	rev.diffopt.skip_stat_unmatch = !!diff_auto_refresh_index;
 
+	/* Default to let external be used */
+	DIFF_OPT_SET(&rev.diffopt, ALLOW_EXTERNAL);
+
 	if (nongit)
 		die("Not a git repository");
 	argc = setup_revisions(argc, argv, &rev, NULL);
@@ -298,7 +301,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 		if (diff_setup_done(&rev.diffopt) < 0)
 			die("diff_setup_done failed");
 	}
-	DIFF_OPT_SET(&rev.diffopt, ALLOW_EXTERNAL);
+
 	DIFF_OPT_SET(&rev.diffopt, RECURSIVE);
 	DIFF_OPT_SET(&rev.diffopt, ALLOW_TEXTCONV);
 

t/t4020-diff-external.sh

@@ -43,6 +43,13 @@ test_expect_success 'GIT_EXTERNAL_DIFF environment should apply only to diff' '
 
 '
 
+test_expect_success 'GIT_EXTERNAL_DIFF environment and --no-ext-diff' '
+
+	GIT_EXTERNAL_DIFF=echo git diff --no-ext-diff |
+	grep "^diff --git a/file b/file"
+
+'
+
 test_expect_success 'diff attribute' '
 
 	git config diff.parrot.command echo &&
@@ -68,6 +75,13 @@ test_expect_success 'diff attribute should apply only to diff' '
 
 '
 
+test_expect_success 'diff attribute and --no-ext-diff' '
+
+	git diff --no-ext-diff |
+	grep "^diff --git a/file b/file"
+
+'
+
 test_expect_success 'diff attribute' '
 
 	git config --unset diff.parrot.command &&
@@ -94,6 +108,13 @@ test_expect_success 'diff attribute should apply only to diff' '
 
 '
 
+test_expect_success 'diff attribute and --no-ext-diff' '
+
+	git diff --no-ext-diff |
+	grep "^diff --git a/file b/file"
+
+'
+
 test_expect_success 'no diff with -diff' '
 	echo >.gitattributes "file -diff" &&
 	git diff | grep Binary