expose NoopChangeToken, NotFoundDirectoryContents, NotFoundFileInfo as public

[Driedas]

changes as per the discussion on issue #145

unit tests passing (executed via dotnet test)

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[dnfclas]

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[pranavkm]

Naming concern since we're making this type public - should this be called NullChangeToken? We name other things similarly e.g. NullLogger for things that don't do much. Thoughts @Eilon ?

[Eilon]

Yeah I suppose this is basically the Null Pattern.

[Eilon]

@pranavkm do we need a bunch of reaction PRs in other repos for this? I suspect this might be a slightly destabilizing change due to other repos needing to react to this.

[Eilon]

Oh actually I wonder if perhaps this is totally safe because the type is moving from being internal in .Sources to being public in the main package. So presumably it's just a switcheroo and perhaps safe...

[pranavkm]

Yeah, the move should be fine and the rename too since it doesn't look like it's used outside of this repo.

[Driedas]

@pranavkm renamed the NoopChangeToken to NullChangeToken and added the comment for NotFoundDirectoryContents, as per your comments
Have tried to come up with a reasonable comment for the NullChangeToken as well, that didn't involve the word "fake" or "stub", as these are mostly associated with *testing, but I have nothing better than "An empty change token that doesn't raise any change callbacks"

[pranavkm]

@Driedas that sounds good.

[pranavkm]

Let me know when you've have added the resx string and I'll merge this in.

[Driedas]

@pranavkm comment added
Do you want me to squash the commits into a single one or is it ok like this?

[pranavkm]

Squashing it would be great.

[Driedas]

done...

[pranavkm]

Thanks!

[Eilon]

@Driedas thanks for the PR!