How do you deal with bugs while developing new features?

As the title suggests...

I have a development server that I develop on. On occasion, I'll find a bug that needs to be fixed, sometimes, I need to fix it right away and deploy to production.

When this happens, I find I have to back out any changes that aren't ready for production, push the fix, then put my changes back in and continue my work.

My build process is a gulp script that pushes everything to a build folder, minifying css, js, etc... but it pushes the entire system. I have no way to selectively say push these 3 files, but not the rest.

After gulp runs and I take a quick look at a staging environment I have setup, an SSH script pushes to the production server.

Is there any "easy" way to push specific files, when they need to be pushed?