I have a master branch and a dev branch. e.g.
master: A--B--C
dev: A--B--C--D--E
then I want to release D and E, so I create a release-1.0 branch from master, squash merge dev to release-1.0, so
release-1.0: A--B--C--F(D&E)
after I release, I merge release-1.0 to master.
master: A--B--C--F(D&E)
then I continue my new changes on dev
dev: A--B--C--D--E--G--H
and conflicts happens when I create release-2.0 from master and merge dev to it.
That's the problem I encountered. I realize this is not the right way to use merge squash, I do some search and didn't find a good solution.
I'd recommend only using regular merges between dev and master. If you really want to squash, you can create a feature branch for it, then squash it into dev once it's done.
Regarding the situation at hand, you can rebase dev commits G and H onto master like this:
git checkout dev
git rebase --onto master <E commit hash>
This is what you'll end up with:
* dbd43d8 (HEAD -> dev) H
* c203a3d G
* 39a258a (master) F(D&E)
* 538454c C
* 8aa2e42 B
* 2f3facb A
Then you can simply fast-forwar merge the master branch.