config.mak.uname: set FREAD_READS_DIRECTORIES for Linux and FreeBSD

This variable is added [1] with the assumption that on a sane system,
fopen(<dir>, "r") should return NULL. Linux and FreeBSD do not meet this
expectation while at least Windows and AIX do. Let's make sure they
behave the same way.

I only tested one version on Linux (4.7.0 with glibc 2.22) and
FreeBSD (11.0) but since GNU/kFreeBSD is fbsd kernel with gnu userspace,
I'm pretty sure it shares the same problem.

[1] cba22528fa (Add compat/fopen.c which returns NULL on attempt to open
    directory - 2008-02-08)

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

config.mak.uname

@@ -36,6 +36,7 @@ ifeq ($(uname_S),Linux)
 	NEEDS_LIBRT = YesPlease
 	HAVE_GETDELIM = YesPlease
 	SANE_TEXT_GREP=-a
+	FREAD_READS_DIRECTORIES = UnfortunatelyYes
 endif
 ifeq ($(uname_S),GNU/kFreeBSD)
 	HAVE_ALLOCA_H = YesPlease
@@ -43,6 +44,7 @@ ifeq ($(uname_S),GNU/kFreeBSD)
 	HAVE_PATHS_H = YesPlease
 	DIR_HAS_BSD_GROUP_SEMANTICS = YesPlease
 	LIBC_CONTAINS_LIBINTL = YesPlease
+	FREAD_READS_DIRECTORIES = UnfortunatelyYes
 endif
 ifeq ($(uname_S),UnixWare)
 	CC = cc
@@ -201,6 +203,7 @@ ifeq ($(uname_S),FreeBSD)
 	GMTIME_UNRELIABLE_ERRORS = UnfortunatelyYes
 	HAVE_BSD_SYSCTL = YesPlease
 	PAGER_ENV = LESS=FRX LV=-c MORE=FRX
+	FREAD_READS_DIRECTORIES = UnfortunatelyYes
 endif
 ifeq ($(uname_S),OpenBSD)
 	NO_STRCASESTR = YesPlease

t/t1308-config-set.sh

@@ -183,6 +183,14 @@ test_expect_success 'proper error on non-existent files' '
 	test_cmp expect actual
 '
 
+test_expect_success 'proper error on directory "files"' '
+	echo "Error (-1) reading configuration file a-directory." >expect &&
+	mkdir a-directory &&
+	test_expect_code 2 test-config configset_get_value foo.bar a-directory 2>output &&
+	grep "^Error" output >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success POSIXPERM,SANITY 'proper error on non-accessible files' '
 	chmod -r .git/config &&
 	test_when_finished "chmod +r .git/config" &&