Implement support for Subversion

[tmat]

• find a cross-platform library that would allow us to gather information from Subversion repository. Preferably, such library would be written entirely in C# (managed code) as having a dependency on native library makes things more complicated.
• determine that all information SourceLink needs can be retrieved from the local repository using the above library
• Implement Microsoft.Build.Tasks.Subversion package
• Implement Microsoft.SourceLink.*.Subversion package for subversion repository providers

[WenningQiu]

@tmat We ran into the same issue. You might want to check out https://www.nuget.org/packages/SourceLink.VisualSVN/1.0.0

[Zastai]

For the second checkbox, it would be useful to list here (or link to) the full set of information needed by sourcelink.

I mean, implementing a version of SourceLink that requires an SVN client in PATH (and an 1.8 or later checkout) could be a start; probably all that would be needed is:

• determine all roots (i.e. all folders with a .svn subdir)
• run svn info on them
  • this could either parse the output (but that might have i18n issues), or run it multiple times, passing --show-item to get a specific value