[Question] Why are dot-prefixed files considered "Sensitive"?

[YuKitsune]

I spent a good amount of time trying to figure out why a Configuration Provider using the PhysicalFileProvider refused to read a dot-prefixed file (E.g. .env).
It turns out, dot-prefixed files are considered sensitive:

runtime/src/libraries/Microsoft.Extensions.FileProviders.Physical/src/ExclusionFilters.cs

Lines 15 to 23 in 75b6c99

	/// <summary>
	/// Equivalent to <c>DotPrefixed | Hidden | System</c>. Exclude files and directories when the name begins with a period, or has either <see cref="FileAttributes.Hidden"/> or <see cref="FileAttributes.System"/> is set on <see cref="FileSystemInfo.Attributes"/>.
	/// </summary>
	Sensitive = DotPrefixed | Hidden | System,
	/// <summary>
	/// Exclude files and directories when the name begins with period.
	/// </summary>
	DotPrefixed = 0x0001,

It was introduced as part of this PR in the previous repository: aspnet/FileSystem#280

After finding this, I had two questions:

1. Why are dot-prefixed files considered sensitive?
2. Why are sensitive files excluded from PhysicalFileProvider by default.

For further context, I'm working on an app where I need to read the configuration from a file called .env. I kept getting FileNotFoundExceptions and had to dig into the source code to find out why.
I've attempted to address the confusing error in this PR: #54717

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Issue Details

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I spent a good amount of time trying to figure out why a Configuration Provider using the PhysicalFileProvider refused to read a dot-prefixed file (E.g. .env). It turns out, dot-prefixed files are considered sensitive.

runtime/src/libraries/Microsoft.Extensions.FileProviders.Physical/src/ExclusionFilters.cs

Lines 15 to 23 in 75b6c99

	/// <summary>
	/// Equivalent to <c>DotPrefixed | Hidden | System</c>. Exclude files and directories when the name begins with a period, or has either <see cref="FileAttributes.Hidden"/> or <see cref="FileAttributes.System"/> is set on <see cref="FileSystemInfo.Attributes"/>.
	/// </summary>
	Sensitive = DotPrefixed | Hidden | System,
	/// <summary>
	/// Exclude files and directories when the name begins with period.
	/// </summary>
	DotPrefixed = 0x0001,

It was introduced in this PR in the previous repository: aspnet/FileSystem#280

Author:	YuKitsune
Assignees:	-
Labels:	area-Extensions-FileSystem, untriaged
Milestone:	-

[adamsitnik]

@blowdart @Tratcher @pranavkm can any of you answer the question?

[blowdart]

Convention. They were hidden from linux directory listings, much like files with the hidden file attribute or system file attribute on Windows. They often contain configuration information. We follow that convention.

This default should not change.

[YuKitsune]

Thanks @blowdart
Not suggesting any changes, just curious as to why they were considered sensitive, and that answers my question 😄