Merge developer to master, it turns out porridge in the show log, why?

Question

Electronic commerce

Good afternoon, I have two master and developer branches, I do all the development in the dev branch and merge it into the master branch in the show log, everything is displayed beautifully and clearly (between the commits in the master branch you can see the sequence of committees in dev ), so for testing the new libraries from the dev branch created another test branch there, made several commits and didn’t have time to test everything I wanted to the end, returned back to the dev branch, made a couple more commits and after merge to the master, show log everything mixed up into a mess (a lot of connections appeared by number commits in the master branch and commits to the master began to be displayed one after another), if you delete the test branch, then the display becomes normal.
In general, how to add the test branch correctly so that the display does not change? I temporarily need the test branch (but for a long time), i.e. it will not merge.
I don’t know how it happened here, I want how test_cgi stayed here

Before merge developer branches in master

This is such a mess, I mainly use the turtle there, I switched to the master branch and did merge to master (it should be git checkout master git merge developer)

I think rather In total, everything is correctly merged, only because of the date or time does it begin to rebuild them in this way.