Merge branch 'jc/dotdot-is-parent-directory' into maint-1.7.11

"git log .." errored out saying it is both rev range and a path when
there is no disambiguating "--" is on the command line.  Update the
command line parser to interpret ".." as a path in such a case.

* jc/dotdot-is-parent-directory:
  specifying ranges: we did not mean to make ".." an empty set

t/t1506-rev-parse-diagnosis.sh

@@ -182,4 +182,18 @@ test_expect_success '<commit>:file correctly diagnosed after a pathname' '
 	test_cmp expect actual
 '
 
+test_expect_success 'dotdot is not an empty set' '
+	( H=$(git rev-parse HEAD) && echo $H && echo ^$H ) >expect &&
+
+	git rev-parse HEAD.. >actual &&
+	test_cmp expect actual &&
+
+	git rev-parse ..HEAD >actual &&
+	test_cmp expect actual &&
+
+	echo .. >expect &&
+	git rev-parse .. >actual &&
+	test_cmp expect actual
+'
+
 test_done

t/t4202-log.sh

@@ -806,4 +806,11 @@ test_expect_success 'log --graph with diff and stats' '
 	test_cmp expect actual.sanitized
 '
 
+test_expect_success 'dotdot is a parent directory' '
+	mkdir -p a/b &&
+	( echo sixth && echo fifth ) >expect &&
+	( cd a/b && git log --format=%s .. ) >actual &&
+	test_cmp expect actual
+'
+
 test_done