[Pending] Finally we add the code linting and its tests! (#2108)

* Lint: PSPossibleIncorrectComparisonWithNull

* Lint: PSUseLiteralInitializerForHashtable

* Lint: PSUseBOMForUnicodeEncodedFile

* Lint: PSUseApprovedVerbs

* Lint: PSAvoidGlobalVars

* Lint: PSAvoidUsingEmptyCatchBlock

* Lint: PSUseShouldProcessForStateChangingFunctions

* Lint helper: Add PSScriptAnalyzer integration for vscode

* Fix lint: PSUseBOMForUnicodeEncodedFile

* Tests: ignore previous TestResults.xml

* Tests: add PowerShell script linting into tests!

* Add PSScriptAnalyzer into appveyor ci

* Update Scoop-Linting.Tests.ps1

PSScriptAnalyzerSettings.psd1

@@ -0,0 +1,37 @@
+# The PowerShell Script Analyzer will generate a warning
+# diagnostic record for this file due to a bug -
+# https://github.com/PowerShell/PSScriptAnalyzer/issues/472
+@{
+    # Only diagnostic records of the specified severity will be generated.
+    # Uncomment the following line if you only want Errors and Warnings but
+    # not Information diagnostic records.
+    Severity = @('Error','Warning')
+
+    # Analyze **only** the following rules. Use IncludeRules when you want
+    # to invoke only a small subset of the defualt rules.
+    # IncludeRules = @('PSAvoidDefaultValueSwitchParameter',
+    #                  'PSMisleadingBacktick',
+    #                  'PSMissingModuleManifestField',
+    #                  'PSReservedCmdletChar',
+    #                  'PSReservedParams',
+    #                  'PSShouldProcess',
+    #                  'PSUseApprovedVerbs',
+    #                  'PSAvoidUsingCmdletAliases',
+    #                  'PSUseDeclaredVarsMoreThanAssignments')
+
+    # Do not analyze the following rules. Use ExcludeRules when you have
+    # commented out the IncludeRules settings above and want to include all
+    # the default rules except for those you exclude below.
+    # Note: if a rule is in both IncludeRules and ExcludeRules, the rule
+    # will be excluded.
+    ExcludeRules = @(
+        # Currently Scoop widely uses Write-Host to output colored text.
+        'PSAvoidUsingWriteHost',
+        # Temporarily allow uses of Invoke-Expression,
+        # this command is used by some core functions and hard to be removed.
+        'PSAvoidUsingInvokeExpression',
+        # PSUseDeclaredVarsMoreThanAssignments doesn't currently work due to:
+        # https://github.com/PowerShell/PSScriptAnalyzer/issues/636
+        'PSUseDeclaredVarsMoreThanAssignments'
+    )
+}