[RFC PATCH 2/2] Switch default hash algorithm to short BLAKE2b for testing

[brian m. carlson]

Set the default hash algorithm to short (160-bit) BLAKE2b so we can
identify tests that rely on a given hash algorithm.

This is a test commit and should not be used in production.  Widespread
test breakage occurs when using this commit.
---
 repository.c  | 2 +-
 setup.c       | 2 +-
 t/test-lib.sh | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/repository.c b/repository.c
index f66fcb1342..95c0ff74d6 100644
--- a/repository.c
+++ b/repository.c
@@ -5,7 +5,7 @@
 
 /* The main repository */
 static struct repository the_repo = {
-       NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &the_index, 
&hash_algos[GIT_HASH_SHA1], 0, 0
+       NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &the_index, 
&hash_algos[GIT_HASH_SBLAKE2], 0, 0
 };
 struct repository *the_repository = &the_repo;
 
diff --git a/setup.c b/setup.c
index 8cc34186ce..72eaee9c4e 100644
--- a/setup.c
+++ b/setup.c
@@ -488,7 +488,7 @@ int read_repository_format(struct repository_format 
*format, const char *path)
        memset(format, 0, sizeof(*format));
        format->version = -1;
        format->is_bare = -1;
-       format->hash_algo = GIT_HASH_SHA1;
+       format->hash_algo = GIT_HASH_SBLAKE2;
        string_list_init(&format->unknown_extensions, 1);
        git_config_from_file(check_repo_format, path, format);
        return format->version;
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 9a0a21f49a..cd257040ad 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -183,8 +183,8 @@ _x40="$_x35$_x05"
 # Zero SHA-1
 _z40=0000000000000000000000000000000000000000
 
-EMPTY_TREE=4b825dc642cb6eb9a060e54bf8d69288fbee4904
-EMPTY_BLOB=e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
+EMPTY_TREE=f44422a644bfa5212387098f253a1e89eba94548
+EMPTY_BLOB=a706650a477f63b9b00eba41272bf36ef5a7dfa2
 
 # Line feed
 LF='