See https://salferrarello.com/wordpress-gitignore/ for the latest version of my WordPress .gitignore file

.gitignore

# -----------------------------------------------------------------
# .gitignore for WordPress
# Bare Minimum Git
# http://ironco.de/bare-minimum-git/
# ver 20150227
#
# This file is tailored for a WordPress project 
# using the default directory structure
#
# This file specifies intentionally untracked files to ignore
# http://git-scm.com/docs/gitignore
#
# NOTES:
# The purpose of gitignore files is to ensure that certain files not
# tracked by Git remain untracked.
#
# To ignore uncommitted changes in a file that is already tracked,
# use `git update-index --assume-unchanged`.
#
# To stop tracking a file that is currently tracked,
# use `git rm --cached`
#
# Change Log:
# 20150227 Ignore hello.php plugin. props @damienfa
# 20150227 Change theme ignore to wildcard twenty*. props @Z33
# 20140606 Add .editorconfig as a tracked file
# 20140404 Ignore database, compiled, and packaged files
# 20140404 Header Information Updated
# 20140402 Initially Published
#
# -----------------------------------------------------------------

# ignore everything in the root except the "wp-content" directory.
/*
!wp-content/

# ignore all files starting with .
.*

# track this file .gitignore (i.e. do NOT ignore it)
!.gitignore

# track .editorconfig file (i.e. do NOT ignore it)
!.editorconfig

# track readme.md in the root (i.e. do NOT ignore it)
!readme.md

# ignore all files that start with ~
~*

# ignore OS generated files
ehthumbs.db
Thumbs.db

# ignore Editor files
*.sublime-project
*.sublime-workspace
*.komodoproject

# ignore log files and databases
*.log
*.sql
*.sqlite

# ignore compiled files
*.com
*.class
*.dll
*.exe
*.o
*.so

# ignore packaged files
*.7z
*.dmg
*.gz
*.iso
*.jar
*.rar
*.tar
*.zip

# ignore everything in the "wp-content" directory, except:
# "mu-plugins" directory
# "plugins" directory
# "themes" directory
wp-content/*
!wp-content/mu-plugins/
!wp-content/plugins/
!wp-content/themes/

# ignore these plugins
wp-content/plugins/hello.php

# ignore specific themes
wp-content/themes/twenty*/

# ignore node/grunt dependency directories
node_modules/