Merge branch 'js/default-branch-name-part-4-minus-1'

Adjust tests so that they won't scream when the default initial
branch name is changed to 'main'.

* js/default-branch-name-part-4-minus-1:
  t1400: prepare for `main` being default branch name
  tests: prepare aligned mentions of the default branch name
  t9902: prepare a test for the upcoming default branch name
  t3200: prepare for `main` being shorter than `master`
  t5703: adjust a test case for the upcoming default branch name
  t6200: adjust suppression pattern to also match "main"
  tests: start moving to a different default main branch name
  t9801: use `--` in preparation for default branch rename
  fmt-merge-msg: also suppress "into main" by default

19 files changed, 130 insertions, 108 deletions

diff --git a/fmt-merge-msg.c b/fmt-merge-msg.c
index bd22e1ea88..9a664a4a58 100644
--- a/fmt-merge-msg.c
+++ b/fmt-merge-msg.c
@@ -626,8 +626,10 @@ int fmt_merge_msg(struct strbuf *in, struct strbuf *out,
 	void *current_branch_to_free;
 	struct merge_parents merge_parents;
 
-	if (!suppress_dest_pattern_seen)
+	if (!suppress_dest_pattern_seen) {
+		string_list_append(&suppress_dest_patterns, "main");
 		string_list_append(&suppress_dest_patterns, "master");
+	}
 
 	memset(&merge_parents, 0, sizeof(merge_parents));
 
diff --git a/refs.c b/refs.c
index fa01153151..392f0bbf68 100644
--- a/refs.c
+++ b/refs.c
@@ -567,8 +567,11 @@ char *repo_default_branch_name(struct repository *r)
 	const char *config_key = "init.defaultbranch";
 	const char *config_display_key = "init.defaultBranch";
 	char *ret = NULL, *full_ref;
+	const char *env = getenv("GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME");
 
-	if (repo_config_get_string(r, config_key, &ret) < 0)
+	if (env && *env)
+		ret = xstrdup(env);
+	else if (repo_config_get_string(r, config_key, &ret) < 0)
 		die(_("could not retrieve `%s`"), config_display_key);
 
 	if (!ret)
diff --git a/t/lib-submodule-update.sh b/t/lib-submodule-update.sh
index 87a759149f..bd3fa3c6da 100644
--- a/t/lib-submodule-update.sh
+++ b/t/lib-submodule-update.sh
@@ -144,7 +144,7 @@ create_lib_submodule_repo () {
 		git checkout -b valid_sub1 &&
 		git revert HEAD &&
 
-		git checkout master
+		git checkout "${GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME-master}"
 	)
 }
 
diff --git a/t/t0001-init.sh b/t/t0001-init.sh
index 2f7c3dcd0f..69a320489f 100755
--- a/t/t0001-init.sh
+++ b/t/t0001-init.sh
@@ -553,14 +553,21 @@ test_expect_success '--initial-branch' '
 
 test_expect_success 'overridden default initial branch name (config)' '
 	test_config_global init.defaultBranch nmb &&
-	git init initial-branch-config &&
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= git init initial-branch-config &&
 	git -C initial-branch-config symbolic-ref HEAD >actual &&
 	grep nmb actual
 '
 
+test_expect_success 'overridden default main branch name (env)' '
+	test_config_global init.defaultBranch nmb &&
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=env git init main-branch-env &&
+	git -C main-branch-env symbolic-ref HEAD >actual &&
+	grep env actual
+'
+
 test_expect_success 'invalid default branch name' '
-	test_config_global init.defaultBranch "with space" &&
-	test_must_fail git init initial-branch-invalid 2>err &&
+	test_must_fail env GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME="with space" \
+		git init initial-branch-invalid 2>err &&
 	test_i18ngrep "invalid branch name" err
 '
 
diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
index 770e7be363..4c01e08551 100755
--- a/t/t1400-update-ref.sh
+++ b/t/t1400-update-ref.sh
@@ -585,10 +585,10 @@ test_expect_success 'stdin fails on unbalanced quotes' '
 	grep "fatal: badly quoted argument: \\\"master" err
 '
 
-test_expect_success 'stdin fails on invalid escape' '
-	echo "create $a \"ma\zter\"" >stdin &&
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'stdin fails on invalid escape' '
+	echo "create $a \"ma\zn\"" >stdin &&
 	test_must_fail git update-ref --stdin <stdin 2>err &&
-	grep "fatal: badly quoted argument: \\\"ma\\\\zter\\\"" err
+	grep "fatal: badly quoted argument: \\\"ma\\\\zn\\\"" err
 '
 
 test_expect_success 'stdin fails on junk after quoted argument' '
@@ -704,9 +704,9 @@ test_expect_success 'stdin succeeds with quoted argument' '
 	test_cmp expect actual
 '
 
-test_expect_success 'stdin succeeds with escaped character' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'stdin succeeds with escaped character' '
 	git update-ref -d $a &&
-	echo "create $a \"ma\\163ter\"" >stdin &&
+	echo "create $a \"ma\\151n\"" >stdin &&
 	git update-ref --stdin <stdin &&
 	git rev-parse $m >expect &&
 	git rev-parse $a >actual &&
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 6efe7a44bc..a0b832d59e 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -321,11 +321,11 @@ test_expect_success 'git branch --list -v with --abbrev' '
 
 '
 
-test_expect_success 'git branch --column' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'git branch --column' '
 	COLUMNS=81 git branch --column=column >actual &&
 	cat >expect <<\EOF &&
-  a/b/c    bam      foo      l      * master   n        o/p      r
-  abc      bar      j/k      m/m      mb       o/o      q        topic
+  a/b/c   bam     foo     l     * main    n       o/p     r
+  abc     bar     j/k     m/m     mb      o/o     q       topic
 EOF
 	test_cmp expect actual
 '
@@ -358,15 +358,15 @@ EOF
 	test_cmp expect actual
 '
 
-test_expect_success 'git branch with column.*' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'git branch with column.*' '
 	git config column.ui column &&
 	git config column.branch "dense" &&
 	COLUMNS=80 git branch >actual &&
 	git config --unset column.branch &&
 	git config --unset column.ui &&
 	cat >expect <<\EOF &&
-  a/b/c   bam   foo   l   * master   n     o/p   r
-  abc     bar   j/k   m/m   mb       o/o   q     topic
+  a/b/c   bam   foo   l   * main   n     o/p   r
+  abc     bar   j/k   m/m   mb     o/o   q     topic
 EOF
 	test_cmp expect actual
 '
@@ -375,9 +375,9 @@ test_expect_success 'git branch --column -v should fail' '
 	test_must_fail git branch --column -v
 '
 
-test_expect_success 'git branch -v with column.ui ignored' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'git branch -v with column.ui ignored' '
 	git config column.ui column &&
-	COLUMNS=80 git branch -v | cut -c -9 | sed "s/ *$//" >actual &&
+	COLUMNS=80 git branch -v | cut -c -8 | sed "s/ *$//" >actual &&
 	git config --unset column.ui &&
 	cat >expect <<\EOF &&
   a/b/c
diff --git a/t/t3201-branch-contains.sh b/t/t3201-branch-contains.sh
index efea5c4971..3733cd0091 100755
--- a/t/t3201-branch-contains.sh
+++ b/t/t3201-branch-contains.sh
@@ -242,7 +242,7 @@ test_expect_success 'branch --merged combined with --no-merged' '
 # Here "topic" tracks "master" with one extra commit, and "zzz" points to the
 # same tip as master The name "zzz" must come alphabetically after "topic"
 # as we process them in that order.
-test_expect_success 'branch --merged with --verbose' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'branch --merged with --verbose' '
 	git branch --track topic master &&
 	git branch zzz topic &&
 	git checkout topic &&
@@ -256,9 +256,9 @@ test_expect_success 'branch --merged with --verbose' '
 	test_cmp expect actual &&
 	git branch --verbose --merged topic >actual &&
 	cat >expect <<-EOF &&
-	  master $(git rev-parse --short master) second on master
-	* topic  $(git rev-parse --short topic ) [ahead 1] foo
-	  zzz    $(git rev-parse --short zzz   ) second on master
+	  main  $(git rev-parse --short main) second on main
+	* topic $(git rev-parse --short topic ) [ahead 1] foo
+	  zzz   $(git rev-parse --short zzz   ) second on main
 	EOF
 	test_i18ncmp expect actual
 '
diff --git a/t/t3203-branch-output.sh b/t/t3203-branch-output.sh
index 71818b90f0..d65586541d 100755
--- a/t/t3203-branch-output.sh
+++ b/t/t3203-branch-output.sh
@@ -329,7 +329,7 @@ test_expect_success '--color overrides auto-color' '
 	test_cmp expect.color actual
 '
 
-test_expect_success 'verbose output lists worktree path' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'verbose output lists worktree path' '
 	one=$(git rev-parse --short HEAD) &&
 	two=$(git rev-parse --short master) &&
 	cat >expect <<-EOF &&
@@ -337,7 +337,7 @@ test_expect_success 'verbose output lists worktree path' '
 	  ambiguous                    $one one
 	  branch-one                   $two two
 	+ branch-two                   $one ($(pwd)/worktree_dir) one
-	  master                       $two two
+	  main                         $two two
 	  ref-to-branch                $two two
 	  ref-to-remote                $two two
 	EOF
diff --git a/t/t3205-branch-color.sh b/t/t3205-branch-color.sh
index 4f1e16bb44..289625c464 100755
--- a/t/t3205-branch-color.sh
+++ b/t/t3205-branch-color.sh
@@ -28,12 +28,12 @@ test_expect_success 'regular output shows colors' '
 	test_cmp expect actual
 '
 
-test_expect_success 'verbose output shows colors' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'verbose output shows colors' '
 	oid=$(git rev-parse --short HEAD) &&
 	cat >expect <<-EOF &&
-	* <CYAN>master               <RESET> $oid foo
-	  <BLUE>other                <RESET> $oid foo
-	  <YELLOW>remotes/origin/master<RESET> $oid foo
+	* <CYAN>main               <RESET> $oid foo
+	  <BLUE>other              <RESET> $oid foo
+	  <YELLOW>remotes/origin/main<RESET> $oid foo
 	EOF
 	git branch --color -v -a >actual.raw &&
 	test_decode_color <actual.raw >actual &&
diff --git a/t/t5505-remote.sh b/t/t5505-remote.sh
index 1156f52069..4b0de6cb83 100755
--- a/t/t5505-remote.sh
+++ b/t/t5505-remote.sh
@@ -213,28 +213,28 @@ cat >test/expect <<EOF
   Push  URL: $(pwd)/one
   HEAD branch: master
   Remote branches:
-    master new (next fetch will store in remotes/origin)
-    side   tracked
+    main new (next fetch will store in remotes/origin)
+    side tracked
   Local branches configured for 'git pull':
-    ahead    merges with remote master
-    master   merges with remote master
+    ahead    merges with remote main
+    main     merges with remote main
     octopus  merges with remote topic-a
                 and with remote topic-b
                 and with remote topic-c
     rebase  rebases onto remote master
   Local refs configured for 'git push':
-    master pushes to master   (local out of date)
-    master pushes to upstream (create)
+    main pushes to main     (local out of date)
+    main pushes to upstream (create)
 * remote two
   Fetch URL: ../two
   Push  URL: ../three
   HEAD branch: master
   Local refs configured for 'git push':
-    ahead  forces to master  (fast-forwardable)
-    master pushes to another (up to date)
+    ahead forces to main    (fast-forwardable)
+    main  pushes to another (up to date)
 EOF
 
-test_expect_success 'show' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'show' '
 	(
 		cd test &&
 		git config --add remote.origin.fetch refs/heads/master:refs/heads/upstream &&
@@ -277,15 +277,15 @@ cat >test/expect <<EOF
     master
     side
   Local branches configured for 'git pull':
-    ahead  merges with remote master
-    master merges with remote master
+    ahead merges with remote main
+    main  merges with remote main
   Local refs configured for 'git push' (status not queried):
     (matching)           pushes to (matching)
-    refs/heads/master    pushes to refs/heads/upstream
+    refs/heads/main      pushes to refs/heads/upstream
     refs/tags/lastbackup forces to refs/tags/lastbackup
 EOF
 
-test_expect_success 'show -n' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'show -n' '
 	mv one one.unreachable &&
 	(
 		cd test &&
@@ -328,7 +328,7 @@ test_expect_success 'set-head --auto' '
 	)
 '
 
-test_expect_success 'set-head --auto has no problem w/multiple HEADs' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'set-head --auto has no problem w/multiple HEADs' '
 	(
 		cd test &&
 		git fetch two "refs/heads/*:refs/remotes/two/*" &&
@@ -1348,7 +1348,7 @@ test_expect_success 'unqualified <dst> refspec DWIM and advice' '
 	)
 '
 
-test_expect_success 'refs/remotes/* <src> refspec and unqualified <dst> DWIM and advice' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'refs/remotes/* <src> refspec and unqualified <dst> DWIM and advice' '
 	(
 		cd two &&
 		git tag -a -m "Some tag" my-tag master &&
diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
index dbc724e4c0..5d673358f9 100755
--- a/t/t5510-fetch.sh
+++ b/t/t5510-fetch.sh
@@ -942,7 +942,7 @@ test_expect_success 'fetching with auto-gc does not lock up' '
 	)
 '
 
-test_expect_success C_LOCALE_OUTPUT 'fetch aligned output' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH,C_LOCALE_OUTPUT 'fetch aligned output' '
 	git clone . full-output &&
 	test_commit looooooooooooong-tag &&
 	(
@@ -951,13 +951,13 @@ test_expect_success C_LOCALE_OUTPUT 'fetch aligned output' '
 		grep -e "->" actual | cut -c 22- >../actual
 	) &&
 	cat >expect <<-\EOF &&
-	master               -> origin/master
+	main                 -> origin/main
 	looooooooooooong-tag -> looooooooooooong-tag
 	EOF
 	test_cmp expect actual
 '
 
-test_expect_success C_LOCALE_OUTPUT 'fetch compact output' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH,C_LOCALE_OUTPUT 'fetch compact output' '
 	git clone . compact &&
 	test_commit extraaa &&
 	(
@@ -966,7 +966,7 @@ test_expect_success C_LOCALE_OUTPUT 'fetch compact output' '
 		grep -e "->" actual | cut -c 22- >../actual
 	) &&
 	cat >expect <<-\EOF &&
-	master     -> origin/*
+	main       -> origin/*
 	extraaa    -> *
 	EOF
 	test_cmp expect actual
diff --git a/t/t5526-fetch-submodules.sh b/t/t5526-fetch-submodules.sh
index 63205dfdf9..dd8e423d25 100755
--- a/t/t5526-fetch-submodules.sh
+++ b/t/t5526-fetch-submodules.sh
@@ -18,7 +18,7 @@ add_upstream_commit() {
 		head2=$(git rev-parse --short HEAD) &&
 		echo "Fetching submodule submodule" > ../expect.err &&
 		echo "From $pwd/submodule" >> ../expect.err &&
-		echo "   $head1..$head2  master     -> origin/master" >> ../expect.err
+		echo "   $head1..$head2  main       -> origin/main" >> ../expect.err
 	) &&
 	(
 		cd deepsubmodule &&
@@ -30,7 +30,7 @@ add_upstream_commit() {
 		head2=$(git rev-parse --short HEAD) &&
 		echo "Fetching submodule submodule/subdir/deepsubmodule" >> ../expect.err
 		echo "From $pwd/deepsubmodule" >> ../expect.err &&
-		echo "   $head1..$head2  master     -> origin/master" >> ../expect.err
+		echo "   $head1..$head2  main       -> origin/main" >> ../expect.err
 	)
 }
 
@@ -61,7 +61,7 @@ test_expect_success setup '
 	)
 '
 
-test_expect_success "fetch --recurse-submodules recurses into submodules" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "fetch --recurse-submodules recurses into submodules" '
 	add_upstream_commit &&
 	(
 		cd downstream &&
@@ -71,7 +71,7 @@ test_expect_success "fetch --recurse-submodules recurses into submodules" '
 	test_i18ncmp expect.err actual.err
 '
 
-test_expect_success "submodule.recurse option triggers recursive fetch" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "submodule.recurse option triggers recursive fetch" '
 	add_upstream_commit &&
 	(
 		cd downstream &&
@@ -81,7 +81,7 @@ test_expect_success "submodule.recurse option triggers recursive fetch" '
 	test_i18ncmp expect.err actual.err
 '
 
-test_expect_success "fetch --recurse-submodules -j2 has the same output behaviour" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "fetch --recurse-submodules -j2 has the same output behaviour" '
 	add_upstream_commit &&
 	(
 		cd downstream &&
@@ -111,7 +111,7 @@ test_expect_success "fetch --no-recurse-submodules only fetches superproject" '
 	test_must_be_empty actual.err
 '
 
-test_expect_success "using fetchRecurseSubmodules=true in .gitmodules recurses into submodules" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "using fetchRecurseSubmodules=true in .gitmodules recurses into submodules" '
 	(
 		cd downstream &&
 		git config -f .gitmodules submodule.submodule.fetchRecurseSubmodules true &&
@@ -141,7 +141,7 @@ test_expect_success "using fetchRecurseSubmodules=false in .git/config overrides
 	test_must_be_empty actual.err
 '
 
-test_expect_success "--recurse-submodules overrides fetchRecurseSubmodules setting from .git/config" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "--recurse-submodules overrides fetchRecurseSubmodules setting from .git/config" '
 	(
 		cd downstream &&
 		git fetch --recurse-submodules >../actual.out 2>../actual.err &&
@@ -170,7 +170,7 @@ test_expect_success "--quiet propagates to parallel submodules" '
 	test_must_be_empty actual.err
 '
 
-test_expect_success "--dry-run propagates to submodules" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "--dry-run propagates to submodules" '
 	add_upstream_commit &&
 	(
 		cd downstream &&
@@ -180,7 +180,7 @@ test_expect_success "--dry-run propagates to submodules" '
 	test_i18ncmp expect.err actual.err
 '
 
-test_expect_success "Without --dry-run propagates to submodules" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "Without --dry-run propagates to submodules" '
 	(
 		cd downstream &&
 		git fetch --recurse-submodules >../actual.out 2>../actual.err
@@ -189,7 +189,7 @@ test_expect_success "Without --dry-run propagates to submodules" '
 	test_i18ncmp expect.err actual.err
 '
 
-test_expect_success "recurseSubmodules=true propagates into submodules" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "recurseSubmodules=true propagates into submodules" '
 	add_upstream_commit &&
 	(
 		cd downstream &&
@@ -200,7 +200,7 @@ test_expect_success "recurseSubmodules=true propagates into submodules" '
 	test_i18ncmp expect.err actual.err
 '
 
-test_expect_success "--recurse-submodules overrides config in submodule" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "--recurse-submodules overrides config in submodule" '
 	add_upstream_commit &&
 	(
 		cd downstream &&
@@ -225,7 +225,7 @@ test_expect_success "--no-recurse-submodules overrides config setting" '
 	test_must_be_empty actual.err
 '
 
-test_expect_success "Recursion doesn't happen when no new commits are fetched in the superproject" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "Recursion doesn't happen when no new commits are fetched in the superproject" '
 	(
 		cd downstream &&
 		(
@@ -239,13 +239,13 @@ test_expect_success "Recursion doesn't happen when no new commits are fetched in
 	test_must_be_empty actual.err
 '
 
-test_expect_success "Recursion stops when no new submodule commits are fetched" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "Recursion stops when no new submodule commits are fetched" '
 	head1=$(git rev-parse --short HEAD) &&
 	git add submodule &&
 	git commit -m "new submodule" &&
 	head2=$(git rev-parse --short HEAD) &&
 	echo "From $pwd/." > expect.err.sub &&
-	echo "   $head1..$head2  master     -> origin/master" >>expect.err.sub &&
+	echo "   $head1..$head2  main       -> origin/main" >>expect.err.sub &&
 	head -3 expect.err >> expect.err.sub &&
 	(
 		cd downstream &&
@@ -255,7 +255,7 @@ test_expect_success "Recursion stops when no new submodule commits are fetched"
 	test_must_be_empty actual.out
 '
 
-test_expect_success "Recursion doesn't happen when new superproject commits don't change any submodules" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "Recursion doesn't happen when new superproject commits don't change any submodules" '
 	add_upstream_commit &&
 	head1=$(git rev-parse --short HEAD) &&
 	echo a > file &&
@@ -263,7 +263,7 @@ test_expect_success "Recursion doesn't happen when new superproject commits don'
 	git commit -m "new file" &&
 	head2=$(git rev-parse --short HEAD) &&
 	echo "From $pwd/." > expect.err.file &&
-	echo "   $head1..$head2  master     -> origin/master" >> expect.err.file &&
+	echo "   $head1..$head2  main       -> origin/main" >> expect.err.file &&
 	(
 		cd downstream &&
 		git fetch >../actual.out 2>../actual.err
@@ -272,7 +272,7 @@ test_expect_success "Recursion doesn't happen when new superproject commits don'
 	test_i18ncmp expect.err.file actual.err
 '
 
-test_expect_success "Recursion picks up config in submodule" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "Recursion picks up config in submodule" '
 	(
 		cd downstream &&
 		git fetch --recurse-submodules &&
@@ -287,7 +287,7 @@ test_expect_success "Recursion picks up config in submodule" '
 	git commit -m "new submodule" &&
 	head2=$(git rev-parse --short HEAD) &&
 	echo "From $pwd/." > expect.err.sub &&
-	echo "   $head1..$head2  master     -> origin/master" >> expect.err.sub &&
+	echo "   $head1..$head2  main       -> origin/main" >> expect.err.sub &&
 	cat expect.err >> expect.err.sub &&
 	(
 		cd downstream &&
@@ -301,7 +301,7 @@ test_expect_success "Recursion picks up config in submodule" '
 	test_must_be_empty actual.out
 '
 
-test_expect_success "Recursion picks up all submodules when necessary" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "Recursion picks up all submodules when necessary" '
 	add_upstream_commit &&
 	(
 		cd submodule &&
@@ -316,14 +316,14 @@ test_expect_success "Recursion picks up all submodules when necessary" '
 		head2=$(git rev-parse --short HEAD) &&
 		echo "Fetching submodule submodule" > ../expect.err.sub &&
 		echo "From $pwd/submodule" >> ../expect.err.sub &&
-		echo "   $head1..$head2  master     -> origin/master" >> ../expect.err.sub
+		echo "   $head1..$head2  main       -> origin/main" >> ../expect.err.sub
 	) &&
 	head1=$(git rev-parse --short HEAD) &&
 	git add submodule &&
 	git commit -m "new submodule" &&
 	head2=$(git rev-parse --short HEAD) &&
 	echo "From $pwd/." > expect.err.2 &&
-	echo "   $head1..$head2  master     -> origin/master" >> expect.err.2 &&
+	echo "   $head1..$head2  main       -> origin/main" >> expect.err.2 &&
 	cat expect.err.sub >> expect.err.2 &&
 	tail -3 expect.err >> expect.err.2 &&
 	(
@@ -334,7 +334,7 @@ test_expect_success "Recursion picks up all submodules when necessary" '
 	test_must_be_empty actual.out
 '
 
-test_expect_success "'--recurse-submodules=on-demand' doesn't recurse when no new commits are fetched in the superproject (and ignores config)" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "'--recurse-submodules=on-demand' doesn't recurse when no new commits are fetched in the superproject (and ignores config)" '
 	add_upstream_commit &&
 	(
 		cd submodule &&
@@ -349,7 +349,7 @@ test_expect_success "'--recurse-submodules=on-demand' doesn't recurse when no ne
 		head2=$(git rev-parse --short HEAD) &&
 		echo Fetching submodule submodule > ../expect.err.sub &&
 		echo "From $pwd/submodule" >> ../expect.err.sub &&
-		echo "   $head1..$head2  master     -> origin/master" >> ../expect.err.sub
+		echo "   $head1..$head2  main       -> origin/main" >> ../expect.err.sub
 	) &&
 	(
 		cd downstream &&
@@ -361,14 +361,14 @@ test_expect_success "'--recurse-submodules=on-demand' doesn't recurse when no ne
 	test_must_be_empty actual.err
 '
 
-test_expect_success "'--recurse-submodules=on-demand' recurses as deep as necessary (and ignores config)" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "'--recurse-submodules=on-demand' recurses as deep as necessary (and ignores config)" '
 	head1=$(git rev-parse --short HEAD) &&
 	git add submodule &&
 	git commit -m "new submodule" &&
 	head2=$(git rev-parse --short HEAD) &&
 	tail -3 expect.err > expect.err.deepsub &&
 	echo "From $pwd/." > expect.err &&
-	echo "   $head1..$head2  master     -> origin/master" >>expect.err &&
+	echo "   $head1..$head2  main       -> origin/main" >>expect.err &&
 	cat expect.err.sub >> expect.err &&
 	cat expect.err.deepsub >> expect.err &&
 	(
@@ -389,7 +389,7 @@ test_expect_success "'--recurse-submodules=on-demand' recurses as deep as necess
 	test_i18ncmp expect.err actual.err
 '
 
-test_expect_success "'--recurse-submodules=on-demand' stops when no new submodule commits are found in the superproject (and ignores config)" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "'--recurse-submodules=on-demand' stops when no new submodule commits are found in the superproject (and ignores config)" '
 	add_upstream_commit &&
 	head1=$(git rev-parse --short HEAD) &&
 	echo a >> file &&
@@ -397,7 +397,7 @@ test_expect_success "'--recurse-submodules=on-demand' stops when no new submodul
 	git commit -m "new file" &&
 	head2=$(git rev-parse --short HEAD) &&
 	echo "From $pwd/." > expect.err.file &&
-	echo "   $head1..$head2  master     -> origin/master" >> expect.err.file &&
+	echo "   $head1..$head2  main       -> origin/main" >> expect.err.file &&
 	(
 		cd downstream &&
 		git fetch --recurse-submodules=on-demand >../actual.out 2>../actual.err
@@ -406,7 +406,7 @@ test_expect_success "'--recurse-submodules=on-demand' stops when no new submodul
 	test_i18ncmp expect.err.file actual.err
 '
 
-test_expect_success "'fetch.recurseSubmodules=on-demand' overrides global config" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "'fetch.recurseSubmodules=on-demand' overrides global config" '
 	(
 		cd downstream &&
 		git fetch --recurse-submodules
@@ -418,7 +418,7 @@ test_expect_success "'fetch.recurseSubmodules=on-demand' overrides global config
 	git commit -m "new submodule" &&
 	head2=$(git rev-parse --short HEAD) &&
 	echo "From $pwd/." > expect.err.2 &&
-	echo "   $head1..$head2  master     -> origin/master" >>expect.err.2 &&
+	echo "   $head1..$head2  main       -> origin/main" >>expect.err.2 &&
 	head -3 expect.err >> expect.err.2 &&
 	(
 		cd downstream &&
@@ -434,7 +434,7 @@ test_expect_success "'fetch.recurseSubmodules=on-demand' overrides global config
 	test_i18ncmp expect.err.2 actual.err
 '
 
-test_expect_success "'submodule.<sub>.fetchRecurseSubmodules=on-demand' overrides fetch.recurseSubmodules" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "'submodule.<sub>.fetchRecurseSubmodules=on-demand' overrides fetch.recurseSubmodules" '
 	(
 		cd downstream &&
 		git fetch --recurse-submodules
@@ -446,7 +446,7 @@ test_expect_success "'submodule.<sub>.fetchRecurseSubmodules=on-demand' override
 	git commit -m "new submodule" &&
 	head2=$(git rev-parse --short HEAD) &&
 	echo "From $pwd/." > expect.err.2 &&
-	echo "   $head1..$head2  master     -> origin/master" >>expect.err.2 &&
+	echo "   $head1..$head2  main       -> origin/main" >>expect.err.2 &&
 	head -3 expect.err >> expect.err.2 &&
 	(
 		cd downstream &&
@@ -462,7 +462,7 @@ test_expect_success "'submodule.<sub>.fetchRecurseSubmodules=on-demand' override
 	test_i18ncmp expect.err.2 actual.err
 '
 
-test_expect_success "don't fetch submodule when newly recorded commits are already present" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "don't fetch submodule when newly recorded commits are already present" '
 	(
 		cd submodule &&
 		git checkout -q HEAD^^
@@ -472,7 +472,7 @@ test_expect_success "don't fetch submodule when newly recorded commits are alrea
 	git commit -m "submodule rewound" &&
 	head2=$(git rev-parse --short HEAD) &&
 	echo "From $pwd/." > expect.err &&
-	echo "   $head1..$head2  master     -> origin/master" >> expect.err &&
+	echo "   $head1..$head2  main       -> origin/main" >> expect.err &&
 	(
 		cd downstream &&
 		git fetch >../actual.out 2>../actual.err
@@ -485,7 +485,7 @@ test_expect_success "don't fetch submodule when newly recorded commits are alrea
 	)
 '
 
-test_expect_success "'fetch.recurseSubmodules=on-demand' works also without .gitmodules entry" '
+test_expect_success PREPARE_FOR_MAIN_BRANCH "'fetch.recurseSubmodules=on-demand' works also without .gitmodules entry" '
 	(
 		cd downstream &&
 		git fetch --recurse-submodules
@@ -497,7 +497,7 @@ test_expect_success "'fetch.recurseSubmodules=on-demand' works also without .git
 	git commit -m "new submodule without .gitmodules" &&
 	head2=$(git rev-parse --short HEAD) &&
 	echo "From $pwd/." >expect.err.2 &&
-	echo "   $head1..$head2  master     -> origin/master" >>expect.err.2 &&
+	echo "   $head1..$head2  main       -> origin/main" >>expect.err.2 &&
 	head -3 expect.err >>expect.err.2 &&
 	(
 		cd downstream &&
diff --git a/t/t5606-clone-options.sh b/t/t5606-clone-options.sh
index 5e201e7d85..7f082fb23b 100755
--- a/t/t5606-clone-options.sh
+++ b/t/t5606-clone-options.sh
@@ -103,6 +103,7 @@ test_expect_success 'redirected clone -v does show progress' '
 
 test_expect_success 'chooses correct default initial branch name' '
 	git init --bare empty &&
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
 	git -c init.defaultBranch=up clone empty whats-up &&
 	test refs/heads/up = $(git -C whats-up symbolic-ref HEAD) &&
 	test refs/heads/up = $(git -C whats-up config branch.up.merge)
@@ -117,9 +118,11 @@ test_expect_success 'guesses initial branch name correctly' '
 
 	git -c init.defaultBranch=none init --bare no-head &&
 	git -C initial-branch push ../no-head guess abc &&
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
 	git clone no-head is-it2 &&
 	test_must_fail git -C is-it2 symbolic-ref refs/remotes/origin/HEAD &&
 	git -C no-head update-ref --no-deref HEAD refs/heads/guess &&
+	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
 	git -c init.defaultBranch=guess clone no-head is-it3 &&
 	test refs/remotes/origin/guess = \
 		$(git -C is-it3 symbolic-ref refs/remotes/origin/HEAD)
diff --git a/t/t5703-upload-pack-ref-in-want.sh b/t/t5703-upload-pack-ref-in-want.sh
index d9ecf0f4a9..b46940b725 100755
--- a/t/t5703-upload-pack-ref-in-want.sh
+++ b/t/t5703-upload-pack-ref-in-want.sh
@@ -383,14 +383,14 @@ test_expect_success 'server is initially behind - ref in want' '
 	test_cmp expected actual
 '
 
-test_expect_success 'server loses a ref - ref in want' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'server loses a ref - ref in want' '
 	git -C "$REPO" config uploadpack.allowRefInWant true &&
 	rm -rf local &&
 	cp -r "$LOCAL_PRISTINE" local &&
-	echo "s/master/raster/" >"$HTTPD_ROOT_PATH/one-time-perl" &&
+	echo "s/main/rain/" >"$HTTPD_ROOT_PATH/one-time-perl" &&
 	test_must_fail git -C local fetch 2>err &&
 
-	test_i18ngrep "fatal: remote error: unknown ref refs/heads/raster" err
+	test_i18ngrep "fatal: remote error: unknown ref refs/heads/rain" err
 '
 
 # DO NOT add non-httpd-specific tests here, because the last part of this
diff --git a/t/t6200-fmt-merge-msg.sh b/t/t6200-fmt-merge-msg.sh
index 7d549748ef..f3e66eaf9b 100755
--- a/t/t6200-fmt-merge-msg.sh
+++ b/t/t6200-fmt-merge-msg.sh
@@ -556,7 +556,7 @@ test_expect_success 'merge.suppressDest configuration' '
 	head -n1 full.2 >actual &&
 	grep -e "Merge branch .side. into master$" actual &&
 
-	git -c merge.suppressDest="ma??er" fmt-merge-msg <.git/FETCH_HEAD >full.3 &&
+	git -c merge.suppressDest="ma?*[rn]" fmt-merge-msg <.git/FETCH_HEAD >full.3 &&
 	head -n1 full.3 >actual &&
 	grep -e "Merge branch .side." actual &&
 	! grep -e " into master$" actual
diff --git a/t/t6302-for-each-ref-filter.sh b/t/t6302-for-each-ref-filter.sh
index 781e470aea..0a21669f56 100755
--- a/t/t6302-for-each-ref-filter.sh
+++ b/t/t6302-for-each-ref-filter.sh
@@ -113,9 +113,9 @@ test_expect_success '%(color) must fail' '
 	test_must_fail git for-each-ref --format="%(color)%(refname)"
 '
 
-test_expect_success 'left alignment is default' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'left alignment is default' '
 	cat >expect <<-\EOF &&
-	refname is refs/heads/master  |refs/heads/master
+	refname is refs/heads/main    |refs/heads/main
 	refname is refs/heads/side    |refs/heads/side
 	refname is refs/odd/spot      |refs/odd/spot
 	refname is refs/tags/annotated-tag|refs/tags/annotated-tag
@@ -131,9 +131,9 @@ test_expect_success 'left alignment is default' '
 	test_cmp expect actual
 '
 
-test_expect_success 'middle alignment' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'middle alignment' '
 	cat >expect <<-\EOF &&
-	| refname is refs/heads/master |refs/heads/master
+	|  refname is refs/heads/main  |refs/heads/main
 	|  refname is refs/heads/side  |refs/heads/side
 	|   refname is refs/odd/spot   |refs/odd/spot
 	|refname is refs/tags/annotated-tag|refs/tags/annotated-tag
@@ -149,9 +149,9 @@ test_expect_success 'middle alignment' '
 	test_cmp expect actual
 '
 
-test_expect_success 'right alignment' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'right alignment' '
 	cat >expect <<-\EOF &&
-	|  refname is refs/heads/master|refs/heads/master
+	|    refname is refs/heads/main|refs/heads/main
 	|    refname is refs/heads/side|refs/heads/side
 	|      refname is refs/odd/spot|refs/odd/spot
 	|refname is refs/tags/annotated-tag|refs/tags/annotated-tag
@@ -168,7 +168,7 @@ test_expect_success 'right alignment' '
 '
 
 cat >expect <<-\EOF
-|       refname is refs/heads/master       |refs/heads/master
+|        refname is refs/heads/main        |refs/heads/main
 |        refname is refs/heads/side        |refs/heads/side
 |         refname is refs/odd/spot         |refs/odd/spot
 |    refname is refs/tags/annotated-tag    |refs/tags/annotated-tag
@@ -184,7 +184,7 @@ EOF
 test_align_permutations() {
 	while read -r option
 	do
-		test_expect_success "align:$option" '
+		test_expect_success PREPARE_FOR_MAIN_BRANCH "align:$option" '
 			git for-each-ref --format="|%(align:$option)refname is %(refname)%(end)|%(refname)" >actual &&
 			test_cmp expect actual
 		'
@@ -213,9 +213,9 @@ EOF
 
 # Individual atoms inside %(align:...) and %(end) must not be quoted.
 
-test_expect_success 'alignment with format quote' "
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'alignment with format quote' "
 	cat >expect <<-\EOF &&
-	|'      '\''master| A U Thor'\''      '|
+	|'       '\''main| A U Thor'\''       '|
 	|'       '\''side| A U Thor'\''       '|
 	|'     '\''odd/spot| A U Thor'\''     '|
 	|'      '\''annotated-tag| '\''       '|
@@ -231,9 +231,9 @@ test_expect_success 'alignment with format quote' "
 	test_cmp expect actual
 "
 
-test_expect_success 'nested alignment with quote formatting' "
+test_expect_success PREPARE_FOR_MAIN_BRANCH 'nested alignment with quote formatting' "
 	cat >expect <<-\EOF &&
-	|'         master               '|
+	|'           main               '|
 	|'           side               '|
 	|'       odd/spot               '|
 	|'  annotated-tag               '|
diff --git a/t/t9801-git-p4-branch.sh b/t/t9801-git-p4-branch.sh
index 67ff2711f5..a3abd778f9 100755
--- a/t/t9801-git-p4-branch.sh
+++ b/t/t9801-git-p4-branch.sh
@@ -67,7 +67,7 @@ test_expect_success 'import main, no branch detection' '
 	(
 		cd "$git" &&
 		git log --oneline --graph --decorate --all &&
-		git rev-list master >wc &&
+		git rev-list master -- >wc &&
 		test_line_count = 4 wc
 	)
 '
@@ -78,7 +78,7 @@ test_expect_success 'import branch1, no branch detection' '
 	(
 		cd "$git" &&
 		git log --oneline --graph --decorate --all &&
-		git rev-list master >wc &&
+		git rev-list master -- >wc &&
 		test_line_count = 2 wc
 	)
 '
@@ -89,7 +89,7 @@ test_expect_success 'import branch2, no branch detection' '
 	(
 		cd "$git" &&
 		git log --oneline --graph --decorate --all &&
-		git rev-list master >wc &&
+		git rev-list master -- >wc &&
 		test_line_count = 2 wc
 	)
 '
@@ -100,7 +100,7 @@ test_expect_success 'import depot, no branch detection' '
 	(
 		cd "$git" &&
 		git log --oneline --graph --decorate --all &&
-		git rev-list master >wc &&
+		git rev-list master -- >wc &&
 		test_line_count = 8 wc
 	)
 '
@@ -114,7 +114,7 @@ test_expect_success 'import depot, branch detection' '
 		git log --oneline --graph --decorate --all &&
 
 		# 4 main commits
-		git rev-list master >wc &&
+		git rev-list master -- >wc &&
 		test_line_count = 4 wc &&
 
 		# 3 main, 1 integrate, 1 on branch2
@@ -137,7 +137,7 @@ test_expect_success 'import depot, branch detection, branchList branch definitio
 		git log --oneline --graph --decorate --all &&
 
 		# 4 main commits
-		git rev-list master >wc &&
+		git rev-list master -- >wc &&
 		test_line_count = 4 wc &&
 
 		# 3 main, 1 integrate, 1 on branch2
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index eb9e56c39e..4e943393cf 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -1055,13 +1055,13 @@ test_expect_success 'teardown after filtering matching refs' '
 	git -C otherrepo branch -D matching/branch-in-other
 '
 
-test_expect_success '__git_refs - for-each-ref format specifiers in prefix' '
+test_expect_success PREPARE_FOR_MAIN_BRANCH '__git_refs - for-each-ref format specifiers in prefix' '
 	cat >expected <<-EOF &&
 	evil-%%-%42-%(refname)..master
 	EOF
 	(
-		cur="evil-%%-%42-%(refname)..mas" &&
-		__git_refs "" "" "evil-%%-%42-%(refname).." mas >"$actual"
+		cur="evil-%%-%42-%(refname)..mai" &&
+		__git_refs "" "" "evil-%%-%42-%(refname).." mai >"$actual"
 	) &&
 	test_cmp expected "$actual"
 '
diff --git a/t/test-lib.sh b/t/test-lib.sh
index f68bca745a..6bc0a30d38 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1705,3 +1705,10 @@ test_lazy_prereq SHA1 '
 test_lazy_prereq REBASE_P '
 	test -z "$GIT_TEST_SKIP_REBASE_P"
 '
+# Special-purpose prereq for transitioning to a new default branch name:
+# Some tests need more than just a mindless (case-preserving) s/master/main/g
+# replacement. The non-trivial adjustments are guarded behind this
+# prerequisite, acting kind of as a feature flag
+test_lazy_prereq PREPARE_FOR_MAIN_BRANCH '
+	test "$GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME" = main
+'