Git: Fatal index.lock error

After typing git commit Filename.file, instead of git commit -m "Your commit message here", I found that I got the error

fatal: Unable to create 'C:/Filepath/.git/index.lock': File exists.

Another git process seems to be running in this repository, e.g.
an editor opened by 'git commit'. Please make sure all processes
are terminated then try again. If it still fails, a git process
may have crashed in this repository earlier:
remove the file manually to continue.

To fix this, I went into Atom, opened the .git folder corresponding with this file, and removed the file index.lock. After doing this, everything worked.

Stack overflow helped fix this issue.

Publishing Jekyll posts

To publish a jekyll post, and get it to show, go through the steps here. The post definitely needs to be inte _posts directory, but the file name and title don’t actually have to match. The .markdown exetension is important. If your post’s date is set in the future, you won’t see the post on locahost:4000, until the time has passed.