UnityのProjectWindowからAssetを選択して右クリックして出たメニューからgithubのページを開いてくれるEditorTool

GitHubPageJumper.cs

using UnityEngine;
using UnityEditor;

public class GitHubPageJumper
{
	// ref https://github.com/p-chin/dotfiles
	private static readonly string gitHubTeamName = "p-chin";
	private static readonly string gitHubRepositoryName = "dotfiles";
	private static readonly string gitHubBranchName = "master";

	[MenuItem("Assets/OpenGithubPage")]
	public static void OpenGitHubPage() {
		string targetPath = GetTargetPath();
		var url = string.Format ("https://github.com/{0}/{1}/blob/{2}/{3}",
			gitHubTeamName, gitHubRepositoryName, gitHubBranchName, targetPath);

		Debug.Log("Open " + url);
		Application.OpenURL (url);
	}

	private static string GetTargetPath()
	{
		Object selected = Selection.objects[0];

		if (selected == null)
		{
			Debug.LogError ("Please select from the file ProjectWindow");
			return null;
		}

		return AssetDatabase.GetAssetPath(selected);;
	}

}