Fix MakeRelative regression in v16.10

[dsparkplug]

Fixes #6493

Replaces PR by @pmisik : #6504

Context

Recent change to MakeRelative function was causing existing targets to fail. The change removed the backslash from the end of paths. This change causes the function to revert to the previous behaviour.

Changes Made

FileUtilities.cs updated

Testing

Added unit tests to FileUtilities_Tests.cs.

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[pmisik]

There is opportunity to extend test coverage for combination of file+directory and directory+file.

/* Directory + File */
 Assert.Equal(@"def", FileUtilities.MakeRelative(@"c:\abc\", @"c:\abc\def"));
 Assert.Equal(@"..\..\def", FileUtilities.MakeRelative(@c:\abc\def\xyz\", @"c:\abc\def"));
 Assert.Equal(@"..\ghi", FileUtilities.MakeRelative(@c:\abc\def\xyz\", @"c:\abc\def\ghi"));
 Assert.Equal(@"..\def", FileUtilities.MakeRelative(@c:\abc\def\", @"c:\abc\def"));

/* File + Directory */
 Assert.Equal(@"def\", FileUtilities.MakeRelative(@c:\abc", @"c:\abc\def\"));
 Assert.Equal(@"..\", FileUtilities.MakeRelative(@c:\abc\def\xyz", @"c:\abc\def\"));
 Assert.Equal(@"..\ghi\", FileUtilities.MakeRelative(@c:\abc\def\xyz", @"c:\abc\def\ghi\"));
 Assert.Equal(@"", FileUtilities.MakeRelative(@c:\abc\def", @"c:\abc\def\"));

[dsparkplug]

Good suggestion - have added more tests

[dsparkplug]

Hmmm.. didn't expect all those commits to be added to the pull request when changing the base branch. And the checks failed too - changing back...

[Forgind]

Looks good! I think I know when this came in—the original uri-based implementation failed tests in the installer repo, for some reason. This version passed those tests and was a bit faster—but also inadvertently changed our behavior with slashes. I don't see why that would be necessary to maintain, so I think this is a good change.

[Forgind]

Oh, and also:
#6504 (comment)

🙂

Is there any reason to keep #6504 around anymore?

[dsparkplug]

The other pr was started by @pmisik - it looks like he has pulled my changes into that and rebased to v16.10 - but it doesn't build for some reason. I really should have based this pr on v16.10 as the fix is needed to fix major dependency issues. Will attempt to base it on v16.10 now - do I need to rebase the source before using the new update to base branch feature?

[dsparkplug]

Have created a new PR #6513 with the same changes squashed and rebased onto vs16.10 branch