t0613: stop setting default initial branch

As the tests are all run in separate repositories, set the branch
name to "master" when creating the repository for the tests where
the result depends on the branch name. In order to make it easier to
change the branch name in the future a helper function is used. This
reduces the number of tests that depend on the default branch name
being "master" and removes the last instance of a test file using
"GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master".

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: phillipwood

t/t0613-reftable-write-options.sh

@@ -11,16 +11,18 @@ export GIT_TEST_REFTABLE_AUTOCOMPACTION
 # Block sizes depend on the hash function, so we force SHA1 here.
 GIT_TEST_DEFAULT_HASH=sha1
 export GIT_TEST_DEFAULT_HASH
-# Block sizes also depend on the actual refs we write, so we force "master" to
-# be the default initial branch name.
-GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master
-export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
 . ./test-lib.sh
 
+# Block sizes depend on the actual refs we write, so, for tests
+# that check block size, we force the initial branch name to be "master".
+init_repo () {
+	git init --initial-branch master repo
+}
+
 test_expect_success 'default write options' '
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -43,7 +45,7 @@ test_expect_success 'default write options' '
 test_expect_success 'disabled reflog writes no log blocks' '
 	test_config_global core.logAllRefUpdates false &&
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -62,7 +64,7 @@ test_expect_success 'disabled reflog writes no log blocks' '
 
 test_expect_success 'many refs results in multiple blocks' '
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -115,7 +117,7 @@ test_expect_success 'tiny block size leads to error' '
 test_expect_success 'small block size leads to multiple ref blocks' '
 	test_config_global core.logAllRefUpdates false &&
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit A &&
@@ -172,7 +174,7 @@ test_expect_success 'block size exceeding maximum supported size' '
 
 test_expect_success 'restart interval at every single record' '
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -212,7 +214,7 @@ test_expect_success 'restart interval exceeding maximum supported interval' '
 test_expect_success 'object index gets written by default with ref index' '
 	test_config_global core.logAllRefUpdates false &&
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -247,7 +249,7 @@ test_expect_success 'object index gets written by default with ref index' '
 test_expect_success 'object index can be disabled' '
 	test_config_global core.logAllRefUpdates false &&
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&