You can, of course, use –exclude and avoid adding the .git folders to your tar archive, but I discovered a really cool option that excludes the folders created by a whole host of version control systems:

--exclude-vcs

Which, as of version 1.32, means excluding CVS, RCS, SCCS, git, SVN, Arch, Bazaar, Mercurial, and Darcs as follows:

• CVS/ — recursive
• RCS/ — recursive
• SCCS/ — recursive
• .git/ — recursive
• .gitignore
• .gitmodules
• .gitattributes
• .cvsignore
• .svn/ — recursive
• .arch-ids/ — recursive
• {arch}/ — recursive
• =RELEASE-ID
• =meta-update
• =update
• .bzr
• .bzrignore
• .bzrtags
• .hg
• .hgignore
• .hgrags
• _darcs