Some useful tools
For full documentation on all the tools provided by the GitHub website and GitHub Desktop, see GitHub's help. Some useful tools you may want to explore include:
- Reverting changes: you can change your mind about something you committed, and revert it to undo it. (Note this will create another commit that reverts an earlier commit.)
- Rolling back to earlier versions: you can roll back your working copy to an older version of your project at any point from the past. For example if you can go back to how your project looked 3 months ago and compare how it looks and works. It's also useful in case anything is accidentally broken, since you can roll back to the last known good version.
- Viewing history: you can see a log of changes to each individual file, with the time they were changed, the commit messages and descriptions for every change, who was changing the file, and so on.
- Blame: the name is a bit unfortunate since hopefully you won't want to use this for accusing people, but Blame breaks down the contents of a file and shows when each part of that file was last changed and by whom. Basically it's just another useful way to look at the history, since you can see when each part of a file was last changed.
- Create branches: a branch is like a variant of your project. For example you could make a branch, and change the menu system. If you don't like it, you can throw away the branch and keep using the old one. If you do like it, you can merge the branch over to the main one (the master branch). This is good for long-term experimental changes, since your in-progress work won't mess up the main branch that everyone else is working on.
- Use other GitHub features like issues, project boards, the wiki and more to help your team work together effectively.
Some Construct-specific advice
Construct assigns UIDs (unique IDs) to objects in the editor. These are saved in the layout files for each instance. By default Construct assigns newly placed instances the lowest unused UID (aka Increment mode as it tends to assign numbers like 1, 2, 3, 4...). This means if two clients who both place a new instance then merge their projects, it's possible the layout file uses the same UID for two objects. Construct tries to handle this gracefully by reassigning duplicated UIDs, but it can still cause issues when using hierarchies or if you refer to specific UIDs in your event sheets. Instead when collaborating on projects it's strongly recommended to change the UID numbering project property to Random. This changes newly assigned UIDs to random numbers with at least six digits, e.g. 582953, 295630, 810344 etc. This means there is a negligible chance that two people create new instances with the same UID.
Also, avoid making manual edits to JSON files in your project. You can edit things like image and sound files outside of Construct and it should use the changes when you next open the project. However if you do something like rename an object by editing the object's JSON file directly, you will most likely corrupt the project. This is because renaming an object actually involves updating a wide range of other references across the project. Construct takes care of this for you when you rename an object from the editor, but if you do this outside of the editor it will create inconsistent references and break the project. When resolving conflicts you may be forced to edit JSON files, and in other cases you might not break anything (like changing the list of instances on a layer). But in general wherever possible you should make changes using the Construct editor to avoid breaking things.
Also note that when Construct updates, make sure everyone on your team updates at the same time. Construct project files are not backwards compatible - i.e. you can't open a project saved in r200 in r100. Similarly, while using source control, you cannot merge changes made in r200 back in to a project saved in r100 and keep using it in r100. Since the file format is not backwards compatible, you may corrupt the project. If everyone on the team updates at the same time, you'll avoid this problem.
Conclusion
Source control software tools like GitHub are mature and advanced tools for effectively collaborating on a project. They are widespread in traditional software development, but source control tools are general-purpose enough that teams using Construct can take advantage of them as well. Since these tools are so well-established and thorough, there should be little need for any specific collaboration features in Construct.
Source control is widely regarded as mandatory for any kind of professional development. Merging by hand is so slow, difficult and error-prone that it is well worth your time to learn source-control tools, even if it seems difficult at first. It's even handy for individual developers for all the additional tools it provides. If you're working in a team, get everyone on source control, and I'm sure before long you'll wonder how you got by without it!