[ethomson]

tl;dr: this is a MSCCI plug-in for git, for compatibility with (quite) old versions of Visual Studio.

This is impressive work. I've used the MSCCI API on several projects - MSCCI is the old version control interface for Visual Studio.

MSCCI is the "Microsoft Source Code Control Interface" and was built to integrate Microsoft Visual SourceSafe into Visual Studio. This was because VSS had a checkout/edit/checkin model by default, so files needed to be explicitly checked out from the server (and were locked) so that they could be modified. MSCCI allowed you to paper over this - as soon as you started typing in the editor, you'd get a MSCCI event and you could do the check out.

Unfortunately, the API is really focused on VSS integration. Trying to bring another version control system into this API is... painful. This was - always - the worst part of the UI to work on in SourceOffSite and Vault.

Thankfully, more modern versions of Visual Studio dropped MSCCI (by "more modern" I mean 2005 - adding Team Foundation Server integration to Visual Studio meant that MSCCI was finally deprecated and a new API was added).

However, legacy development projects exist for older Microsoft platforms and using older Visual Studio versions. So I'm both surprised to see that this exists, and am rather heartened by its existence. (But I still feel sorry for anybody who has to use it.)