In VMS, revision control was built into the file system. It was easy to retrieve older versions of files. Unix didn't have anything like that until rcs was invented, and even then it was a tool, not something built in like what VMS had.
"The /VERSION_LIMIT qualifier for the CREATE/DIRECTORY, SET DIRECTORY, and SET FILE commands lets you control the number of versions of a file. If you exceed the version limit, the system automatically purges the lowest version file in excess of the limit. For example, if the version limit is 5 and you create the sixth version of a file (ACCOUNTS.DAT;6), the system deletes the first version of the file (ACCOUNTS.DAT;1). To view the version limit on a file, enter the DIRECTORY/FULL command. The version limit is listed in the File attributes: field."
OpenVMS Manual http://h41379.www4.hpe.com/doc/731final/6489/6489pro_006.htm...
I thoroughly enjoyed using DCL (Digital Command Line -- the VMS shell) and VMS (with the wall of documentation, like http://www.pkl.net/~matt/photos/machines/tn/pict0157.jpg.htm...). It always felt structured and orderly, unlike UNIX systems, which are more "organic". :) (I love UNIX too!)
git checkout filename.c;2