Add fixtures.

git-date/tests/fixtures/generate_git_date_baseline.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+set -eu -o pipefail
+
+git init;
+
+function baseline() {
+    local test_date=$1 # first argument is the date to test
+
+    git -c section.key="$test_date" config --type=expiry-date section.key && status=0 || status=$?
+#    git ls-files "$pathspec" && status=0 || status=$?
+    {
+        echo "$test_date"
+        echo "$status"
+    } >> baseline.git
+}
+
+# success
+
+# date formats following to https://git-scm.com/docs/git-log#Documentation/git-log.txt---dateltformatgt
+# short
+baseline '2022-08-22'
+# rfc2822
+baseline 'Thu, 18 Aug 2022 12:45:06 +0800'
+# iso8601
+baseline '2022-08-17 22:04:58 +0200'
+# iso8601_strict
+baseline '2022-08-17T21:43:13+08:00'
+# default
+baseline 'Thu Sep 04 2022 10:45:06 -0400'
+# unix
+baseline '123456789'
+# raw
+baseline '1660874655 +0800'
+
+# failing
+
+# empty_input
+baseline ""
+