repository: enable SHA-256 support by default

Now that we have a complete SHA-256 implementation in Git, let's enable
it so people can use it.  Remove the ENABLE_SHA256 define constant
everywhere it's used.  Add tests for initializing a repository with
SHA-256.

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

builtin/init-db.c

@@ -183,11 +183,6 @@ void initialize_repository_version(int hash_algo)
 	char repo_version_string[10];
 	int repo_version = GIT_REPO_VERSION;
 
-#ifndef ENABLE_SHA256
-	if (hash_algo != GIT_HASH_SHA1)
-		die(_("The hash algorithm %s is not supported in this build."), hash_algos[hash_algo].name);
-#endif
-
 	if (hash_algo != GIT_HASH_SHA1)
 		repo_version = GIT_REPO_VERSION_READ;
 

config.mak.dev

@@ -16,8 +16,6 @@ DEVELOPER_CFLAGS += -Wstrict-prototypes
 DEVELOPER_CFLAGS += -Wunused
 DEVELOPER_CFLAGS += -Wvla
 
-DEVELOPER_CFLAGS += -DENABLE_SHA256
-
 ifndef COMPILER_FEATURES
 COMPILER_FEATURES := $(shell ./detect-compiler $(CC))
 endif

repository.c

@@ -89,10 +89,6 @@ void repo_set_gitdir(struct repository *repo,
 void repo_set_hash_algo(struct repository *repo, int hash_algo)
 {
 	repo->hash_algo = &hash_algos[hash_algo];
-#ifndef ENABLE_SHA256
-	if (hash_algo != GIT_HASH_SHA1)
-		die(_("The hash algorithm %s is not supported in this build."), repo->hash_algo->name);
-#endif
 }
 
 /*

t/t0001-init.sh

@@ -441,6 +441,39 @@ test_expect_success 're-init from a linked worktree' '
 	)
 '
 
+test_expect_success 'init honors GIT_DEFAULT_HASH' '
+	GIT_DEFAULT_HASH=sha1 git init sha1 &&
+	git -C sha1 rev-parse --show-object-format >actual &&
+	echo sha1 >expected &&
+	test_cmp expected actual &&
+	GIT_DEFAULT_HASH=sha256 git init sha256 &&
+	git -C sha256 rev-parse --show-object-format >actual &&
+	echo sha256 >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'init honors --object-format' '
+	git init --object-format=sha1 explicit-sha1 &&
+	git -C explicit-sha1 rev-parse --show-object-format >actual &&
+	echo sha1 >expected &&
+	test_cmp expected actual &&
+	git init --object-format=sha256 explicit-sha256 &&
+	git -C explicit-sha256 rev-parse --show-object-format >actual &&
+	echo sha256 >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'extensions.objectFormat is not allowed with repo version 0' '
+	git init --object-format=sha256 explicit-v0 &&
+	git -C explicit-v0 config core.repositoryformatversion 0 &&
+	test_must_fail git -C explicit-v0 rev-parse --show-object-format
+'
+
+test_expect_success 'init rejects attempts to initialize with different hash' '
+	test_must_fail git -C sha1 init --object-format=sha256 &&
+	test_must_fail git -C sha256 init --object-format=sha1
+'
+
 test_expect_success MINGW 'core.hidedotfiles = false' '
 	git config --global core.hidedotfiles false &&
 	rm -rf newdir &&