I have forked a project and doing some changes on it during several commits. I want to know if I submit a merge request, history of all commits are available to maintainer or not?
I'm looking for a solution which all commits are aggregated as one commit and I don't know if it does happen during merge request or not? This is because I have do some trial-n-errors and I don't like that these trial-n-errors be visible to project maintainer.
Yes, if you push your branch, all the history will be there. You can either
#1 Squash all your commits before you push your branch: see Git: How to squash all commits on branch how to do this
or
#2 Squash all your commits on merge: newer versions of gitlab have a feature that if you merge to master, all your commits will be automatically squashed before the actual merge:
See https://docs.gitlab.com/ee/user/project/merge_requests/squash_and_merge.html for more information.
Personally I have done #1 before Gitlab could merge automatically. Now I do #2 all the time. If you don't want the history of all your commits available to the maintaner, you should do #1. Otherwise #2 will work just fine and the end result will be the same: One single commit for your changes.
Yes, whatever you push, it will be the whole history up there. Some people like to squash commits before doing that. I see a lot of people using git rebase -i or git merge --squash for that. I like to do it by hand this way... say it's 10 commits you want to squash:
git reset --soft HEAD~10
git commit -m "blah blah"
Voila! There you have a squashed commit.
