Pushing content and theme folders to GitHub

I'm following Alison Hill's workflow from her post, but got hung up at the stage of pushing the content and themes directories to GitHub. Just these 2. Everything else was transferred easily. However, for either of these directories, an index.lock file appears in the .git subdirectory and everything in RStudio freezes. I need to shut down RStudio and then reopen it (new session doesn't work) and use the terminal to remove the offending file with the "rm -f .git/index.lock" command recommended in Stack Overflow. Is there anything different from the other directories about these directories? All the various blogdown checks have been done and all recommendations implemented (although none appear to have much to do with this freeze). Any advice? Thanks, Jim Hunter