[PATCH v2] show-index: fix uninitialized hash function

[Abhijeet Sonar <abhijeet.nkt@gmail.com>]

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 <abhijeet.nkt@gmail.com>
---
 builtin/show-index.c                |  3 +++
 t/t8101-show-index-hash-function.sh | 15 +++++++++++++++
 2 files changed, 18 insertions(+)
 create mode 100755 t/t8101-show-index-hash-function.sh

diff --git a/builtin/show-index.c b/builtin/show-index.c
index 540dc3dad1..bb6d9e3c40 100644
--- a/builtin/show-index.c
+++ b/builtin/show-index.c
@@ -35,6 +35,9 @@ int cmd_show_index(int argc, const char **argv, const char *prefix)
 		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)
diff --git a/t/t8101-show-index-hash-function.sh b/t/t8101-show-index-hash-function.sh
new file mode 100755
index 0000000000..2e9308f73c
--- /dev/null
+++ b/t/t8101-show-index-hash-function.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+
+test_description='git show-index'
+
+. ./test-lib.sh
+
+test_expect_success 'show-index: should not fail outside a repository' '
+    git init --object-format=sha1 && (
+        echo "" | git hash-object -w --stdin | git pack-objects test &&
+        rm -rf .git &&
+        cat test-*.idx | git show-index
+    )
+'
+
+test_done
-- 
2.45.2.827.g557ae147e6