Recently I've been getting duplicate package windows opening up when I debug
an SSIS solution. This is a problem because if I edit the wrong files then I
find that my changes weren't saved when I next open the package.

The only difference I can see is in the icons associated with the files in
the open file dropdown. One version of the package has the same icon as in
the project (faint grey control-flow-like image and a bright blue square in
the bottom right corner), while the other version has three blue squares
arranged in a lower case r shape (as opposed to J, L or 7) with a not so
bright blue square in the bottom right corner.

Hovering over these icons gives me absolutely zero info about what they
mean. I suspect it's something to do with source control? Can anyone
enlighten me?

Ta in advance,
David