Hey Jay,
In case you’re still having problems with this, it seems like the (tagged) build in the official WordPress plugin repo isn’t quite the same as the 1.3.3 tagged version in github:
$ diff -r benbalter-WP-Document-Revisions-5bdbf54/ wp-document-revisions/
Only in benbalter-WP-Document-Revisions-5bdbf54/: .gitmodules
Only in wp-document-revisions/: menu-icon.png
Only in wp-document-revisions/tests: test-file-2.txt
Only in wp-document-revisions/tests: test-file.txt
Only in wp-document-revisions/tests/wordpress-tests: all.php
Only in wp-document-revisions/tests/wordpress-tests: bootstrap.php
Only in wp-document-revisions/tests/wordpress-tests: documents
Only in wp-document-revisions/tests/wordpress-tests: functions.php
Only in wp-document-revisions/tests/wordpress-tests: phpunit.xml
Only in wp-document-revisions/tests/wordpress-tests: test_document_front_end.php
Only in wp-document-revisions/tests/wordpress-tests: test_document_revisions.php
Only in wp-document-revisions/tests/wordpress-tests: test_document_rewrites.php
Only in wp-document-revisions/tests/wordpress-tests: wordpress-tests
I was receiving the same error message you saw when trying to add wp-content/plugins/wp-document-revisions/ to my project’s git repo after installing it through the WordPress interface. After replacing the downloaded version with an extracted tar of 1.3.3 from Github the plugin was added to my git repo as expected.
Hope this helps.