Fix 2755: msvs tool, msvs tests, and msvc detection fixes

[jcbrill]

Fixes:

• Fixes Make the VS tool less intrusive of the SCONS_HOME variable #2755: the msvs tool no longer writes the OS environment SCONS_HOME value into the SCons environment when the SCONS_HOME variable already exists in the SCons environment.
• Update the windows registry keys for detection of Visual Studio 2015 Express ('14.0Exp'): the VS2015 registry key (WDExpress) appears to be different than the registry key (VCExpress) for earlier Visual Studio express versions.
• Fix the vs-6.0-exec.py test script: the msvs generated project is foo.dsp and the command-line invocation of the Visual Studio development environment program was attempting to build test.dsp.
• Update the msvs project generation test scripts: the msvs project execution tests could produce a false positive test result when the test executable is correctly built via the SConstruct env.Program() call and the command-line invocation of the Visual Studio development environment program fails.
• Add method unlink_files to TestCmd class that unlinks a list of files from a specified directory. Add test cases for unlink_files to TestCmdtTests.

No documentation changes were necessary.

Contributor Checklist:

• I have created a new test or updated the unit tests to cover the new/changed functionality.
• I have updated CHANGES.txt (and read the README.rst)
• I have updated the appropriate documentation

[bdbaddog]

Can you move this into TestSConsMSVS? rather than copy/pasting it into all the files?

[jcbrill]

Sure.

[jcbrill]

Should it be a function that takes a list of files?

Something like:

test.remove_files(['foo.exe', 'foo.obj', 'sconsign.dblite'])

[bdbaddog]

Does scons -c not do this?

[jcbrill]

Pretty sure it also removes the generated msvs project.

[jcbrill]

Would the following be acceptable?

TestSConsMSVS.py

    def unlink_files(self, filedir, filenames):
        for filename in filenames:
            filepath = self.workpath(filedir, filename)
            if os.path.exists(filepath):
                self.unlink(filepath)

test scripts:

test.unlink_files('sub dir', ['foo.exe', 'foo.obj', '.sconsign.dblite'])

[bdbaddog]

does scons -c not remove the files in question?

[jcbrill]

I'm pretty sure that scons -c removes the generated msvs project which needs to be built from the command-line with the msdev binary. There will be no project to pass to the command-line after "scons -c" is run.

The sequence is:

• scons SConstruct (generates msvs project and builds program)
• delete program binaries
• pathto\msdev.com foo.dsp to build the program binaries via the generated workspace.

[bdbaddog]

gotcha. ok so it's not about cleaning all the build products, but rather removing those which should be built when you have msvs run the created project file.

Ok. I'd add that method to TestCmd.py where there are currently other file handling functions, rather than TestSConsMSVS, as it could be useful for non MSVC tests.

[jcbrill]

Changes:

1. Added rewritten unlink_files to TestCmd class with docstring and functionality consistent with unlink method.
2. Replaced all msvs executable script deletion loops with single test method call.
3. Reordered authors alphabetically in CHANGES.txt,

The following are all equivalent:

test.unlink_files('sub dir', ['foo.exe', 'foo.obj', '.sconsign.dblite'])
test.unlink_files(['sub dir'], ['foo.exe', 'foo.obj', '.sconsign.dblite'])
test.unlink_files('', [['sub dir', 'foo.exe'], ['sub dir', 'foo.obj'], ['sub dir', '.sconsign.dblite']])
test.unlink_files([''], [['sub dir', 'foo.exe'], ['sub dir', 'foo.obj'], ['sub dir', '.sconsign.dblite']])
test.unlink_files('.', [['sub dir', 'foo.exe'], ['sub dir', 'foo.obj'], ['sub dir', '.sconsign.dblite']])
test.unlink_files(['.'], [['sub dir', 'foo.exe'], ['sub dir', 'foo.obj'], ['sub dir', '.sconsign.dblite']])

[jcbrill]

No additional work is planned.

[bdbaddog]

Look good. Merging!