[CMake] Enhancing the Visual Studio Generators' Source Control integration

[Steven Velez]

Hi All,

We have noticed, that using the VS_SCC_* target properties, we can
bind to a perforce SCM server.  However, the way that SCC works the
perforce plugin has to prompt the user for connection information.
When we were doing this with hand-made visual studio solutions, we
would only be prompted once when the workspace was fresh and clean,
and the information would be retained thereafter.  With our
CMake-generated solutions, we are prompted on every invocation of
visual studio.  We'd like to get back to the fewer prompts workflow.

After much research and trial and error, we have discovered that this
seems to be because the bindings created by cmake are stored in the
visual studio project files...and only there.  It seems that a more
complete binding also records some SCC-related properties in the
solution file...

Therefore, I started hacking on the visual studio generator to try and
decipher how this functionality would be added to cmake, and made good
progress.  However, there are some solution file properties related to
SCC that must be recorded for the solution itself.  For most entries,
I can just query the targets' VS_SCC_ properties, but there are no
such properties for the solution/project.   What's more, is there is
no existing precedent, that I can find, for user-specified project
properties.  So I am not sure how I would be able to give the user
control over what these properties may be.  In my scenario, with the
perforce SCC plugin, I _could_ get the necessary properties form the
first target, but I doubt this is the general solution otherwise there
is simply too much redundancy in the protocol/format.

Long question short... is there an existing, reliable way for the user
to provide per-project properties that the generator can get at?

Thanks,
Steven