show-index: fix uninitialized hash function

As stated in the docs, show-index should use SHA1 as the default hash algorithm
when run outsize of a repository.  However, 'the_hash_algo' is currently left
uninitialized if we are not in a repository and no explicit hash function is
specified, causing a crash.  Fix it by falling back to SHA1 when it is found
uninitialized. Also add test that verifies this behaviour.

Signed-off-by: Abhijeet Sonar <[email protected]>
Signed-off-by: Taylor Blau <[email protected]>

Author: quanta-kt

builtin/show-index.c

@@ -38,6 +38,9 @@ int cmd_show_index(int argc,
 		repo_set_hash_algo(the_repository, hash_algo);
 	}
 
+	if (!the_hash_algo)
+		repo_set_hash_algo(the_repository, GIT_HASH_SHA1);
+
 	hashsz = the_hash_algo->rawsz;
 
 	if (fread(top_index, 2 * 4, 1, stdin) != 1)

t/t5300-pack-object.sh

@@ -523,6 +523,10 @@ test_expect_success 'index-pack --strict <pack> works in non-repo' '
 	test_path_is_file foo.idx
 '
 
+test_expect_success SHA1 'show-index works OK outside a repository' '
+	nongit git show-index <foo.idx
+'
+
 test_expect_success !PTHREADS,!FAIL_PREREQS \
 	'index-pack --threads=N or pack.threads=N warns when no pthreads' '
 	test_must_fail git index-pack --threads=2 2>err &&