rev-parse: tests git rev-parse --verify master@{n}, for various n

This commit introduces tests that verify that rev-parse
parses master@{n} correctly for various values of n less
than, equal to and greater than the number of revisions
in the reference log.

In particular, these tests check that rev-parse exits with a
non-zero status code and prints a message of the
following form to stderr.

    fatal: Log for [^ ]* only has [0-9][0-9]* entries.

Signed-off-by: Jon Seymour <jon.seymour@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1503-rev-parse-verify.sh

@@ -104,4 +104,15 @@ test_expect_success 'use --default' '
 	test_must_fail git rev-parse --verify --default bar
 '
 
+test_expect_success 'master@{n} for various n' '
+	N=$(git reflog | wc -l) &&
+	Nm1=$((N-1)) &&
+	Np1=$((N+1)) &&
+	git rev-parse --verify master@{0} &&
+	git rev-parse --verify master@{1} &&
+	git rev-parse --verify master@{$Nm1} &&
+	test_must_fail "git rev-parse --verify master@{$N}" &&
+	test_must_fail "git rev-parse --verify master@{$Np1}"
+'
+
 test_done

t/t1506-rev-parse-diagnosis.sh

@@ -66,4 +66,13 @@ test_expect_success 'incorrect file in :path and :N:path' '
 	grep "fatal: Path '"'"'disk-only.txt'"'"' exists on disk, but not in the index." error
 '
 
+test_expect_success 'invalid @{n} reference' '
+	test_must_fail git rev-parse master@{99999} >output 2>error &&
+	test -z "$(cat output)" &&
+	grep "fatal: Log for [^ ]* only has [0-9][0-9]* entries." error  &&
+	test_must_fail git rev-parse --verify master@{99999} >output 2>error &&
+	test -z "$(cat output)" &&
+	grep "fatal: Log for [^ ]* only has [0-9][0-9]* entries." error
+'
+
 test_done