What happens if we make conflicting changes to a file?
Take a look at the file planning/stage1.MD. This contains a list of steps that would need to be undertaken to refurbish the kitchen;
1. Install the cupboards
1. Install the drawers
1. Paint the ceiling
1. Tile the walls
1. Install the counter tops
1. Install the oven
1. Install the fridgeI am now going to change this file on the original upstream repository. I have decided we will use an electric oven, so I will edit the file to contain;
1. Install the cupboards
1. Install the drawers
1. Paint the ceiling
1. Tile the walls
1. Install the counter tops
1. Install the electric oven
1. Install the fridge(note I have changed oven to electric oven)
I am now going to commit this change, and will push that to the original upstream repository.
I have changed planning/stage1.MD in the original upstream repository. This has not made any changes to your forked repository. You can show this by typing;
git pullto pull any changes that have been made to your forked repository. You should see that there are no changes. If you open your copy of planning/stage1.MD you should see that it still contains;
1. Install the ovenOk - let’s say that you don’t know that I have decided that the oven should be electric (or don’t agree that it should). You want to use a gas oven. Edit your copy of planning/stage1.MD and change it to contain;
1. Install the cupboards
1. Install the drawers
1. Paint the ceiling
1. Tile the walls
1. Install the counter tops
1. Install the gas oven
1. Install the fridge(you will change oven to gas oven)
Commit the change using git commit -a and push it to your fork using git push. So far, so good :-)
There is now a difference between your fork (which uses a gas oven) and the original upstream repository (which uses an electric oven). This is a problem, as now there is a conflict when you try to pull new changes that have been made in upstream.
Type;
git pull upstream mainYou should see output that looks something like this;
remote: Enumerating objects: 7, done.
remote: Counting objects: 100% (7/7), done.
remote: Compressing objects: 100% (1/1), done.
remote: Total 4 (delta 2), reused 4 (delta 2), pack-reused 0
Unpacking objects: 100% (4/4), done.
From https://github.com/chryswoods/super_project
* branch main -> FETCH_HEAD
4ebc762..455bb5e main -> upstream/main
Auto-merging planning/stage1.MD
CONFLICT (content): Merge conflict in planning/stage1.MD
Automatic merge failed; fix conflicts and then commit the result.The last lines are important. They say that git has seen that there is a conflict in planning/stage1.MD. Git does its best to merge changes, but it cannot do so automatically when the changes both occur on the same line. In this case, you have to fix the conflict manually, but merging the two changes into one.
To do this, you need to edit planning/stage1.MD again. You will see that git has changed this file, with the lines around the conflict now looking something like this;
1. Install the cupboards
1. Install the drawers
1. Paint the ceiling
1. Tile the walls
1. Install the counter tops
<<<<<<< HEAD
1. Install the gas oven
=======
1. Install the electric oven
>>>>>>> 455bb5eb6b71ddb5970d7d2d9016b8aeb67afab6
1. Install the fridgeGit has put both versions of the conflicted line into the file. These are marked using the following symbols
<<<<<<< HEAD - this means that the following lines are the ones that came from your working copy======= - this separates lines from your computer and the lines from the remote version>>>>>>> 455bb5eb6b71ddb5970d7d2d9016b8aeb67afab6 - this means that the following lines are the ones that came from the remote version, with the specified git commit number.You now have to decide how to merge the conflicted lines together. In some cases that could mean looking for a compromise, or reworking the file so that there is no real conflict.
In this case, there is no compromise between installing an electric or gas oven, so, for now, choose a gas oven, as this is what you wanted. Edit the file to contain;
1. Install the cupboards
1. Install the drawers
1. Paint the ceiling
1. Tile the walls
1. Install the counter tops
1. Install the gas oven
1. Install the fridge(you have removed the other conflicted line, plus removed the symbols that git inserted)
Now you have resolved the conflict, you can commit the file using git commit -a. Note that git has automatically detected that you are committing a merge, and has pre-populated the commit message with something like;
Merge branch 'main' of https://github.com/chryswoods/super_project into main
# Conflicts:
# planning/stage1.MD
#
# It looks like you may be committing a merge.
# If this is not correct, please remove the file
# .git/MERGE_HEAD
# and try again.You can now push this commit to your fork of super_project via git push.
Note that you have now resolved this conflict, so you can use git pull upstream main to fetch new changes to upstream without worrying about this conflict again. However, your fork is now working on a plan to install a gas oven, while I am working in upstream and am planning to install an electric oven… Far from resolving the conflict, we have just pushed the problem down the road…
For now, you will keep planning on installing a gas oven. To do this, we will need to plan for gas to be installed in the kitchen. Make a change to planning/stage1.MD and add steps for installing gas and a gas boiler, e.g.
1. Install a gas pipe
1. Install a gas boiler
1. Install the cupboards
1. Install the drawers
1. Paint the ceiling
1. Tile the walls
1. Install the counter tops
1. Install the gas oven
1. Install the fridgeCommit the change and push this to your fork (git commit -a followed by git push).
Meanwhile, I am going to plan for an electric boiler to be installed, as I will have an electric oven…
1. Install an electric boiler
1. Install the cupboards
1. Install the drawers
1. Paint the ceiling
1. Tile the walls
1. Install the counter tops
1. Install the electric oven
1. Install the fridgeI will commit and push this to the original upstream repository…
Now that I have done this, pull the changes I’ve made into your working directory via git pull upstream main. Again, you should see that git reports a conflict in planning/stage1.MD. Looking at this file shows;
<<<<<<< HEAD
1. Install a gas pipe
1. Install a gas boiler
=======
1. Install an electric boiler
>>>>>>> ccace0204c938d5e3880d39d81a276a676101133You can see that I am still pressing ahead with the electric kitchen, while you are working with the gas kitchen. Again, you should resolve the conflict by restoring your original lines, e.g.
1. Install a gas pipe
1. Install a gas boilerand then committing and pushing them to your fork (git commit -a and git push).
Again, this is a temporary fix, and it is just pushing this bigger decision (gas or electric?) further down the road. Even worse, what happens if I now make a change that doesn’t conflict, but which assumes we are using an electric boiler? For example, I will now add in the installation of electric heaters, e.g.
1. Install an electric boiler
1. Install electric heaters
1. Install the cupboards
1. Install the drawers
1. Paint the ceiling
1. Tile the walls
1. Install the counter tops
1. Install the electric oven
1. Install the fridgeand I will commit and push those changes.
Now, when you git pull upstream main you may find that either my new electric heaters line is added to your file, or that you see yet another conflict that will need to be resolved, e.g.
<<<<<<< HEAD
1. Install a gas pipe
1. Install a gas boiler
=======
1. Install an electric boiler
1. Install electric heaters
>>>>>>> 23b0083d757f7f3ae00cc743ff43988feb61bb8fAt this point, rather than continuing to resolve and merge, it may be worth using the greatest tool of conflict resolution - namely communication, which will look at on the next page.
Resolve the conflict by changing electric heaters to radiators. Commit and push your change to your fork.