branch name in `doInitialCommit` function push command

[gmlwo530]

I am using initial branch name to main. And, i set this name in git configure file(ex. ~/.gitconfig on macos).

So, i think that command of doInitialCommit should be changed.

It would be nice to change it to use the name returned by the init.defaultBranch.

commands := []initialCommands{
		...
		{
			description: "git push -u origin master",
			command:     "git",
			args:        []string{"push", "-u", "origin", "master"},
		},
}

[bmonkman]

We use main for all our repositories as well, thanks for noticing this oversight!