* test: fix test failure in case of different default branch
When the git config has set global `init.defaultBranch` different than master,
a few test cases were failing.
Currently, the test case is assuming the default branch to be set as
master.
This commit will introduce **initial_branch** option to git init call
which will ensure *master* branch is used as default for out test cases.
Set default git branch to main for test CI
Since main is going to be new default branch, it will let the test case
handle the scenario where default branch is set other than master.
Introduce isolation for git configuration
Co-authored-by: Saugat Pachhai (सौगात) <[email protected]>
