[git] Git subtree install option

[tsuga]

This PR enhances the existing git feature to install git/contrib/subtree by specifying to do so in the options.

    "options": {
        "version": {
            "type": "string",
            "proposals": [
                "latest",
                "system",
                "os-provided"
            ],
            "default": "os-provided",
            "description": "Select or enter a Git version."
        },
        "ppa": {
            "type": "boolean",
            "default": true,
            "description": "Install from PPA if available (only supported for Ubuntu distributions)"
        },
        "installSubtree": {
            "type": "boolean",
            "default": false,
            "description": "Install git/contrib/subtree"
        }
    },

[tsuga]

@microsoft-github-policy-service agree

[samruddhikhandale]

Hi @tsuga 👋

Thank you for taking the time to contribute this PR. Can you help me understand how you utilize git/contrib/subtree and how impactful this change will be for the community?

I understand that the git-subtree command is an alternative to git-submodule for managing project dependencies. However, we'd like more feedback before we add this feature option. Hope that makes sense to you. Thanks!

// cc @bamurtaugh

[tsuga]

Hi @samruddhikhandale
There are various pros and cons over subtree vs submodule.
You may find good explanation on the Internet.

[Karmaibringkaosanddrama]

This PR enhances the existing git feature to install git/contrib/subtree by specifying to do so in the options.

    "options": {
        "version": {
            "type": "string",
            "proposals": [
                "latest",
                "system",
                "os-provided"
            ],
            "default": "os-provided",
            "description": "Select or enter a Git version."
        },
        "ppa": {
            "type": "boolean",
            "default": true,
            "description": "Install from PPA if available (only supported for Ubuntu distributions)"
        },
        "installSubtree": {
            "type": "boolean",
            "default": false,
            "description": "Install git/contrib/subtree"
        }
    },

@