t: skip pack tests if not using SHA-1

These tests rely on creating packs with specially named objects which
are necessarily dependent on the hash used.  Skip these tests if we're
not using SHA-1.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5308-pack-detect-duplicates.sh

@@ -4,6 +4,12 @@ test_description='handling of duplicate objects in incoming packfiles'
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-pack.sh
 
+if ! test_have_prereq SHA1
+then
+       skip_all='not using SHA-1 for objects'
+       test_done
+fi
+
 # The sha1s we have in our pack. It's important that these have the same
 # starting byte, so that they end up in the same fanout section of the index.
 # That lets us make sure we are exercising the binary search with both sets.

t/t5309-pack-delta-cycles.sh

@@ -4,6 +4,12 @@ test_description='test index-pack handling of delta cycles in packfiles'
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-pack.sh
 
+if ! test_have_prereq SHA1
+then
+       skip_all='not using SHA-1 for objects'
+       test_done
+fi
+
 # Two similar-ish objects that we have computed deltas between.
 A=01d7713666f4de822776c7622c10f1b07de280dc
 B=e68fe8129b546b101aee9510c5328e7f21ca1d18