my thought is that you did a git merge of some sort, git had a conflict, and it left a message in one of those files that starts or contains that text, jekyll is seeing it and is saying hey wait - there is no such file called git rev-parse whatever.
just open those files and read them and see if there is something in there probably at the top in the front matter that has that text.
If there is nothing like that in those files try searching the whole repo if you are using sublime do a find in files for git rev-parse and see if it is in a file somewhere.
I’m not saying that this is it, just worth checking. I am no git expert but I think I screwed up once and ended up with something like this.