When merging branches, you need to guide Git on how to resolve conflicting changes in different branches.
A merge conflict happens when Git can't automatically combine changes from two branches because the same parts of a file were modified differently in each branch. When this happens, Git pauses the merge and marks the conflicting sections in the affected files so you can resolve them yourself. Once you've reviewed and fixed the conflicts, you can tell Git they're resolved and complete the merge.
More generally, a conflict occurs when Git cannot automatically reconcile different changes made to the same part of a file -- branch merge conflicts is just one example.
In this hands-on practical, we simulate a merge conflict and use it to learn how to resolve merge conflicts. You can use any repo with at least one commit in the master branch for this.
1 Start a branch named fix1 in the repo. Create a commit that adds a line with some text to one of the files.
2 Switch back to master branch. Create a commit with a conflicting change i.e. it adds a line with some different text in the exact location the previous line was added.
3 Try to merge the fix1 branch onto the master branch. Git will pause mid-way during the merge and report a merge conflict. If you open the conflicted file, you will see something like this:
COLORS
------
blue
<<<<<< HEAD
black
=======
green
>>>>>> fix1
red
white
4 Observe how the conflicted part is marked between a line starting with <<<<<< and a line starting with >>>>>>, separated by another line starting with =======.
Highlighted below is the conflicting part that is coming from the master branch:
blue
<<<<<< HEAD
black
=======
green
>>>>>> fix1
red
This is the conflicting part that is coming from the fix1 branch:
blue
<<<<<< HEAD
black
=======
green
>>>>>> fix1
red
5 Resolve the conflict by editing the file. Let us assume you want to keep both lines in the merged version. You can modify the file to be like this:
COLORS
------
blue
black
green
red
white
6 Stage the changes, and commit. You have now successfully resolved the merge conflict.