I tried that too before posting, but unsuccessful:
MyMac:myproj1 SM$ bower install driftyco/ionic-bower#1.2.1-nightly-1867
bower not-cached git://github.com/driftyco/ionic-bower.git#1.2.1
bower resolve git://github.com/driftyco/ionic-bower.git#1.2.1
bower not-cached git://github.com/driftyco/ionic-bower.git#1.2.1-nightly-1867
bower resolve git://github.com/driftyco/ionic-bower.git#1.2.1-nightly-1867
bower download https://github.com/driftyco/ionic-bower/archive/v1.2.1-nightly-1867.tar.gz
bower extract ionic-bower#1.2.1-nightly-1867 archive.tar.gz
bower invalid-meta ionic is missing "ignore" entry in bower.json
bower resolved git://github.com/driftyco/ionic-bower.git#1.2.1-nightly-1867
bower ENORESTARGET No tag found that was able to satisfy 1.2.1
What are we doing differently? Here is my system info:
Cordova CLI: 5.4.1
Ionic CLI Version: 1.7.12
Ionic App Lib Version: 0.6.5
ios-deploy version: Not installed
ios-sim version: Not installed
OS: Mac OS X El Capitan
Node Version: v5.2.0
Xcode version: Not installed