test suite: Provide tstunt/debchange

This uses faketime to get the date right, like t-dch does.
It has to be requested with t-tstunt debchange, which nothing does
yet, so NFC.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/tests/tstunt/debchange b/tests/tstunt/debchange
new file mode 100755 (executable)
index 0000000..8c81823
--- /dev/null
+++ b/tests/tstunt/debchange
@@ -0,0 +1,4 @@
+#!/bin/sh
+set -x
+faketime @"${GIT_AUTHOR_DATE% *}" \
+"$DGIT_TEST_REAL_DEBCHANGE" "$@"