[PATCH v10 1/8] t/t5505-remote: set default branch to main

Consider the bare repository called "mirror" in the test. Running `git remote add --mirror -f origin ../one` will not change HEAD, consequently if init.defaultBranch is not the same as what HEAD in the remote ("one"), HEAD in "mirror" will be pointing to a non-existent reference. Hence if "mirror" is used as a remote by yet another repository, ls-remote will not show HEAD. On the other hand, if init.defaultBranch happens to match HEAD in "one", then ls-remote will show HEAD.

Since the CI globally exports GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main, there's a drift between how the test repositories are set up in the CI and during local testing. This issue does not manifest currently, as the test does not do any remote HEAD manipulation where this would come up, but should such things be added, a locally passing test would break the CI vice-versa.

Set GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main in the test to be consistent with the CI. ---

Notes:
    v9: - new patch
        - a bandaid for the CI issue noticed by Taylor (cf:
          https://lore.kernel.org/git/Zw8IKyPkG0Hr6%2F5t@nand.local/), but
          see
          https://lore.kernel.org/git/D4ZAELFWJMKN.S88LJ6YK31LZ@ferdinandy.com/ for the root cause in detail
    
    v10: no change

 t/t5505-remote.sh | 3 +++
 1 file changed, 3 insertions(+)