I created branch "task-1" from branch "master", did some changes then committed and pushed those.
It went all fine when doing this on sourcetree. But then when I go on BitBucket, I did a Pull Request. There I noticed that a conflict was notified.
I thought I did a mistake when using sourcetree. Looked at my commit, then reset my commit and try again. Same issue!
In the end, I could not find why BitBucket would signal a conflict. And I thought "ok, let's try to merge the "task-1" branch into "master" branch locally, maybe I'll be able to fix the conflict locally more easily somehow. Surprise: no conflict had to be resolved locally, "task-1" merged smoothly into "master" branch.
See attached screenshot for conflict on BitBucket