whitespace: fix off-by-one error in non-space-in-indent checking

If there were no tabs, and the last space was at position 7, then
positions 0..7 had spaces, so there were 8 spaces.

Update test to check exactly this case.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4015-diff-whitespace.sh

@@ -298,7 +298,7 @@ test_expect_success 'check space before tab in indent (space-before-tab: on)' '
 test_expect_success 'check spaces as indentation (indent-with-non-tab: off)' '
 
 	git config core.whitespace "-indent-with-non-tab"
-	echo "                foo ();" > x &&
+	echo "        foo ();" > x &&
 	git diff --check
 
 '
@@ -306,7 +306,7 @@ test_expect_success 'check spaces as indentation (indent-with-non-tab: off)' '
 test_expect_success 'check spaces as indentation (indent-with-non-tab: on)' '
 
 	git config core.whitespace "indent-with-non-tab" &&
-	echo "                foo ();" > x &&
+	echo "        foo ();" > x &&
 	! git diff --check
 
 '

ws.c

@@ -159,7 +159,7 @@ unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
 	}
 
 	/* Check for indent using non-tab. */
-	if ((ws_rule & WS_INDENT_WITH_NON_TAB) && leading_space >= 8)
+	if ((ws_rule & WS_INDENT_WITH_NON_TAB) && leading_space >= 7)
 		result |= WS_INDENT_WITH_NON_TAB;
 
 	if (stream) {