tests: mark tests relying on the current default for `init.defaultBranch`

tests: mark tests relying on the current default for `init.defaultBranch`

In addition to the manual adjustment to let the `linux-gcc` CI job run
the test suite with `master` and then with `main`, this patch makes sure
that GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME is set in all test scripts
that currently rely on the initial branch name being `master by default.

To determine which test scripts to mark up, the first step was to
force-set the default branch name to `master` in

- all test scripts that contain the keyword `master`,

- t4211, which expects `t/t4211/history.export` with a hard-coded ref to
  initialize the default branch,

- t5560 because it sources `t/t556x_common` which uses `master`,

- t8002 and t8012 because both source `t/annotate-tests.sh` which also
  uses `master`)

This trick was performed by this command:

	$ sed -i '/^ *\. \.\/\(test-lib\|lib-\(bash\|cvs\|git-svn\)\|gitweb-lib\)\.sh$/i\
	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master\
	export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME\
	' $(git grep -l master t/t[0-9]*.sh) \
	t/t4211*.sh t/t5560*.sh t/t8002*.sh t/t8012*.sh

After that, careful, manual inspection revealed that some of the test
scripts containing the needle `master` do not actually rely on a
specific default branch name: either they mention `master` only in a
comment, or they initialize that branch specificially, or they do not
actually refer to the current default branch. Therefore, the
aforementioned modification was undone in those test scripts thusly:

	$ git checkout HEAD -- \
		t/t0027-auto-crlf.sh t/t0060-path-utils.sh \
		t/t1011-read-tree-sparse-checkout.sh \
		t/t1305-config-include.sh t/t1309-early-config.sh \
		t/t1402-check-ref-format.sh t/t1450-fsck.sh \
		t/t2024-checkout-dwim.sh \
		t/t2106-update-index-assume-unchanged.sh \
		t/t3040-subprojects-basic.sh t/t3301-notes.sh \
		t/t3308-notes-merge.sh t/t3423-rebase-reword.sh \
		t/t3436-rebase-more-options.sh \
		t/t4015-diff-whitespace.sh t/t4257-am-interactive.sh \
		t/t5323-pack-redundant.sh t/t5401-update-hooks.sh \
		t/t5511-refspec.sh t/t5526-fetch-submodules.sh \
		t/t5529-push-errors.sh t/t5530-upload-pack-error.sh \
		t/t5548-push-porcelain.sh \
		t/t5552-skipping-fetch-negotiator.sh \
		t/t5572-pull-submodule.sh t/t5608-clone-2gb.sh \
		t/t5614-clone-submodules-shallow.sh \
		t/t7508-status.sh t/t7606-merge-custom.sh \
		t/t9302-fast-import-unpack-limit.sh

We excluded one set of test scripts in these commands, though: the range
of `git p4` tests. The reason? `git p4` stores the (foreign) remote
branch in the branch called `p4/master`, which is obviously not the
default branch. Manual analysis revealed that only five of these tests
actually require a specific default branch name to pass; They were
modified thusly:

	$ sed -i '/^ *\. \.\/lib-git-p4\.sh$/i\
	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master\
	export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME\
	' t/t980[0167]*.sh t/t9811*.sh

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>