At first glance it might appear SSMS 2017 no longer supports third party source controls only because the Tools, Options menu no longer displays the Source Control section.
However, it turns out it is quite easy to tweak the SSMS 2017 configuration to restore those missing Source Control configuration options as described below.
The test described below was done using the SSMS v17.4 release:
Step 1. With SSMS not running, open up a command prompt in administrator mode and make a backup copy of the SSMS configuration file shown below, copying it to a safe location just in case:
C:\Program Files (x86)\Microsoft SQL Server\140\Tools\Binn\ManagementStudio\ssms.pkgundef
Step 2. From that command prompt edit the SSMS configuration file using notepad.exe; located the Visual SourceSafe entries and remove the three entires usign the // *** line comments as indicated in the text below:
// TFS SCC Configuration entries. The TFS entries block Team Explorer from loading.
// Microsoft.VisualStudio.TeamFoundation.VersionControl.HatPackage
[$RootKey$\AutoLoadPackages\{4CA58AB2-18FA-4F8D-95D4-32DDF27D184C}]
// Microsoft.VisualStudio.TeamFoundation.Lab
[$RootKey$\Packages\{17c5d08a-602c-4dfb-82b5-8e0f7f50c9d7}]
// GitHub Package
[$RootKey$\Packages\{c3d3dc68-c977-411f-b3e8-03b0dccf7dfc}]
// Team Foundation Server Provider Package
[$RootKey$\Packages\{5BF14E63-E267-4787-B20B-B814FD043B38}]
// Microsoft.VisualStudio.TeamFoundation.WorkItemTracking.WitPcwPackage
[$RootKey$\Packages\{6238f138-0c0c-49ec-b24b-215ee59d84f0}]
// Microsoft.VisualStudio.TeamFoundation.Build.BuildPackage
[$RootKey$\Packages\{739f34b3-9ba6-4356-9178-ac3ea81bdf47}]
// Microsoft.VisualStudio.TeamFoundation.WorkItemTracking
[$RootKey$\Packages\{ca39e596-31ed-4b34-aa36-5f0240457a7e}]
// Microsoft.VisualStudio.TeamFoundation
[$RootKey$\Packages\{b80b010d-188c-4b19-b483-6c20d52071ae}]
// Microsoft.TeamFoundation.Git.Provider.SccProviderPackage
[$RootKey$\Packages\{7fe30a77-37f9-4cf2-83dd-96b207028e1b}]
// Microsoft.VisualStudio.TeamFoundation.VersionControl.SccPcwPluginPackage
[$RootKey$\Packages\{1b4f495a-280a-3ba4-8db0-9c9b735e98ce}]
// Microsoft.VisualStudio.TeamFoundation.VersionControl.HatPackage
[$RootKey$\Packages\{4CA58AB2-18FA-4F8D-95D4-32DDF27D184C}]
// Visual SourceSafe Provider Package
// *** [$RootKey$\Packages\{AA8EB8CD-7A51-11D0-92C3-00A0C9138C45}] <===== Comment out this line ****
// Visual SourceSafe Provider Stub Package
// *** [$RootKey$\Packages\{53544C4D-B03D-4209-A7D0-D9DD13A4019B}] <===== Comment out this line ****
// Microsoft.VisualStudio.TeamFoundation.Initialization.InitializationPackage
[$RootKey$\Packages\{75DF55D4-EC28-47FC-88AC-BE56203C9012}]
// Team Foundation Server Provider Stub Package
[$RootKey$\Packages\{D79B7E0A-F994-4D4D-8FAE-CAE147279E21}]
// Microsoft.VisualStudio.Services.SccDisplayInformationPackage
[$RootKey$\Packages\{D7BB9305-5804-4F92-9CFE-119F4CB0563B}]
// Microsoft.VisualStudio.TeamFoundation.Lab.LabPcwPluginPackage
[$RootKey$\Packages\{e0910062-da1f-411c-b152-a3fc6392ee1f}]
// *** [$RootKey$\ToolsOptionsPages\Source Control] <===== Comment out this line ****
[$RootKey$\AutoLoadPackages\{11b8e6d7-c08b-4385-b321-321078cdd1f8}]
// TFS SCC Configuration entries.
Step 3. Save the file changes, start SSMS 2017 and now the Source Control section is once again accessible by using the Tools, Options menu:
IMPORTANT: If that Source Control option is missing it means the MS-SCCI source control components are not installed.
To get these missing components installed will require the installation of the Visual Studio 2015 IDE as that installer will add in these components.
Alternatively the Visual Studio 2015 Community Editon can also be used. A web search will locate that free download.
Step 4. To make sure all the componets mentioned earlier are in fact installed, select Source Control section shown below:
If that panel does not show correctly it means the Visual Studio 2015 components are not installed.
Step 5. With those changes made just create a SSMS project and start adding the items to source control: