Merge branch 'ps/setup-reinit-fixes'

"git init" to reinitialize a repository that already exists cannot
change the hash function and ref backends; such a request is
silently ignored now.

* ps/setup-reinit-fixes:
  setup: fix reinit of repos with incompatible GIT_DEFAULT_HASH
  setup: fix reinit of repos with incompatible GIT_DEFAULT_REF_FORMAT
  t0001: remove duplicate test

Author: gitster

setup.c

@@ -2517,7 +2517,9 @@ static void repository_format_configure(struct repository_format *repo_fmt,
 		int env_algo = hash_algo_by_name(env);
 		if (env_algo == GIT_HASH_UNKNOWN)
 			die(_("unknown hash algorithm '%s'"), env);
-		repo_fmt->hash_algo = env_algo;
+		if (repo_fmt->version < 0 ||
+		    repo_fmt->hash_algo == GIT_HASH_UNKNOWN)
+			repo_fmt->hash_algo = env_algo;
 	} else if (cfg.hash != GIT_HASH_UNKNOWN) {
 		repo_fmt->hash_algo = cfg.hash;
 	}
@@ -2534,7 +2536,9 @@ static void repository_format_configure(struct repository_format *repo_fmt,
 		ref_format = ref_storage_format_by_name(env);
 		if (ref_format == REF_STORAGE_FORMAT_UNKNOWN)
 			die(_("unknown ref storage format '%s'"), env);
-		repo_fmt->ref_storage_format = ref_format;
+		if (repo_fmt->version < 0 ||
+		    repo_fmt->ref_storage_format == REF_STORAGE_FORMAT_UNKNOWN)
+			repo_fmt->ref_storage_format = ref_format;
 	} else if (cfg.ref_format != REF_STORAGE_FORMAT_UNKNOWN) {
 		repo_fmt->ref_storage_format = cfg.ref_format;
 	}

t/t0001-init.sh

@@ -586,6 +586,18 @@ test_expect_success 'GIT_DEFAULT_HASH overrides init.defaultObjectFormat' '
 	echo sha256 >expected
 '
 
+for hash in sha1 sha256
+do
+	test_expect_success "reinit repository with GIT_DEFAULT_HASH=$hash does not change format" '
+		test_when_finished "rm -rf repo" &&
+		git init repo &&
+		git -C repo rev-parse --show-object-format >expect &&
+		GIT_DEFAULT_HASH=$hash git init repo &&
+		git -C repo rev-parse --show-object-format >actual &&
+		test_cmp expect actual
+	'
+done
+
 test_expect_success 'extensions.objectFormat is not allowed with repo version 0' '
 	test_when_finished "rm -rf explicit-v0" &&
 	git init --object-format=sha256 explicit-v0 &&
@@ -697,6 +709,15 @@ do
 		git -C refformat rev-parse --show-ref-format >actual &&
 		test_cmp expect actual
 	'
+
+	test_expect_success "reinit repository with GIT_DEFAULT_REF_FORMAT=$format does not change format" '
+		test_when_finished "rm -rf refformat" &&
+		git init refformat &&
+		git -C refformat rev-parse --show-ref-format >expect &&
+		GIT_DEFAULT_REF_FORMAT=$format git init refformat &&
+		git -C refformat rev-parse --show-ref-format >actual &&
+		test_cmp expect actual
+	'
 done
 
 test_expect_success "--ref-format= overrides GIT_DEFAULT_REF_FORMAT" '
@@ -861,15 +882,6 @@ test_expect_success 're-init with includeIf.onbranch condition' '
 	test_cmp expect actual
 '
 
-test_expect_success 're-init with includeIf.onbranch condition' '
-	test_when_finished "rm -rf repo" &&
-	git init repo &&
-	git -c includeIf.onbranch:nonexistent.path=/does/not/exist init repo &&
-	echo $GIT_DEFAULT_REF_FORMAT >expect &&
-	git -C repo rev-parse --show-ref-format >actual &&
-	test_cmp expect actual
-'
-
 test_expect_success 're-init skips non-matching includeIf.onbranch' '
 	test_when_finished "rm -rf repo config" &&
 	cat >config <<-EOF &&