Jonathan Nieder [off-list ref] writes:
The most recent example I can find is 2010:
http://public-inbox.org/git/4C6A1C5B.4030304@workspacewhiz.com/.
It also came up in 2007:
http://public-inbox.org/git/C0E9F681E68D48EB8989022D11FEE3D1@ntdev.corp.microsoft.com/
Earlier in that year it even made the "What's not in 1.5.2" list.
http://public-inbox.org/git/11793556383977-git-send-email-junkio@cox.net/
Perhaps those references could be a useful starting point for an
interested person's thinking.
Thanks for links. It seems that my thinking back in 1.5.3 timeperiod
was to introduce "precious" attribute.
I noticed that among the four-message "What's not in 1.5.2" series,
3/4 has a large discussion that may be relevant to Brandon's
"submodule is-active" thing.