Adds opt-in precommit hook to check formatting.

.swift-format-nolint

@@ -0,0 +1,68 @@
+{
+  "fileScopedDeclarationPrivacy" : {
+    "accessLevel" : "private"
+  },
+  "indentation" : {
+    "spaces" : 4
+  },
+  "indentConditionalCompilationBlocks" : false,
+  "indentSwitchCaseLabels" : false,
+  "lineBreakAroundMultilineExpressionChainComponents" : false,
+  "lineBreakBeforeControlFlowKeywords" : false,
+  "lineBreakBeforeEachArgument" : false,
+  "lineBreakBeforeEachGenericRequirement" : false,
+  "lineLength" : 180,
+  "maximumBlankLines" : 1,
+  "multiElementCollectionTrailingCommas" : true,
+  "noAssignmentInExpressions" : {
+    "allowedFunctions" : [
+      "XCTAssertNoThrow"
+    ]
+  },
+  "prioritizeKeepingFunctionOutputTogether" : false,
+  "respectsExistingLineBreaks" : true,
+  "rules" : {
+    "AllPublicDeclarationsHaveDocumentation" : false,
+    "AlwaysUseLowerCamelCase" : false,
+    "AmbiguousTrailingClosureOverload" : false,
+    "BeginDocumentationCommentWithOneLineSummary" : false,
+    "DoNotUseSemicolons" : true,
+    "DontRepeatTypeInStaticProperties" : false,
+    "FileScopedDeclarationPrivacy" : false,
+    "FullyIndirectEnum" : false,
+    "GroupNumericLiterals" : false,
+    "IdentifiersMustBeASCII" : false,
+    "NeverForceUnwrap" : false,
+    "NeverUseForceTry" : false,
+    "NeverUseImplicitlyUnwrappedOptionals" : false,
+    "NoAccessLevelOnExtensionDeclaration" : false,
+    "NoAssignmentInExpressions" : false,
+    "NoBlockComments" : false,
+    "NoCasesWithOnlyFallthrough" : false,
+    "NoEmptyTrailingClosureParentheses" : true,
+    "NoLabelsInCasePatterns" : false,
+    "NoLeadingUnderscores" : false,
+    "NoParensAroundConditions" : true,
+    "NoPlaygroundLiterals" : false,
+    "NoVoidReturnOnFunctionSignature" : true,
+    "OmitExplicitReturns" : false,
+    "OneCasePerLine" : true,
+    "OneVariableDeclarationPerLine" : true,
+    "OnlyOneTrailingClosureArgument" : false,
+    "OrderedImports" : true,
+    "ReplaceForEachWithForLoop" : false,
+    "ReturnVoidInsteadOfEmptyTuple" : false,
+    "TypeNamesShouldBeCapitalized" : false,
+    "UseEarlyExits" : false,
+    "UseLetInEveryBoundCaseVariable" : false,
+    "UseShorthandTypeNames" : true,
+    "UseSingleLinePropertyGetter" : true,
+    "UseSynthesizedInitializer" : false,
+    "UseTripleSlashForDocumentationComments" : true,
+    "UseWhereClausesInForLoops" : false,
+    "ValidateDocumentationComments" : false
+  },
+  "spacesAroundRangeFormationOperators" : false,
+  "tabWidth" : 2,
+  "version" : 1
+}

Makefile

@@ -126,6 +126,9 @@ ifeq (,$(wildcard bin/vmlinux))
 	@cp .local/vmlinux bin/vmlinux
 endif
 
+.PHONY: check
+check: swift-fmt-check check-licenses
+
 .PHONY: fmt
 fmt: swift-fmt update-licenses
 
@@ -135,6 +138,10 @@ swift-fmt:
 	@echo Applying the standard code formatting...
 	@$(SWIFT) format --recursive --configuration .swift-format -i $(SWIFT_SRC)
 
+swift-fmt-check:
+	   @echo Applying the standard code formatting...
+	   @$(SWIFT) format lint --recursive --strict --configuration .swift-format-nolint $(SWIFT_SRC)
+
 .PHONY: update-licenses
 update-licenses:
 	@echo Updating license headers...
@@ -147,6 +154,15 @@ check-licenses:
 	@./scripts/ensure-hawkeye-exists.sh
 	@.local/bin/hawkeye check --fail-if-unknown
 
+.PHONY: pre-commit
+pre-commit:
+	   cp Scripts/pre-commit.fmt .git/hooks
+	   touch .git/hooks/pre-commit
+	   cat .git/hooks/pre-commit | grep -v 'hooks/pre-commit\.fmt' > /tmp/pre-commit.new || true
+	   echo 'PRECOMMIT_NOFMT=$${PRECOMMIT_NOFMT} $$(git rev-parse --show-toplevel)/.git/hooks/pre-commit.fmt' >> /tmp/pre-commit.new
+	   mv /tmp/pre-commit.new .git/hooks/pre-commit
+	   chmod +x .git/hooks/pre-commit
+
 .PHONY: serve-docs
 serve-docs:
 	@echo 'to browse: open http://127.0.0.1:8000/containerization/documentation/'

README.md

@@ -145,6 +145,10 @@ make protos
 
 If you'd like to build your own kernel please see the instructions in the [kernel directory](./kernel/README.md).
 
+## Pre-commit hook
+
+Run `make pre-commit` to install a pre-commit hook that ensures that your changes have correct formatting and license headers when you run `git commit`.
+
 ## Documentation
 
 Generate the API documentation for local viewing with:

Sources/ContainerizationOCI/Platform.swift

@@ -194,20 +194,18 @@ public struct Platform: Sendable, Equatable {
 }
 
 extension Platform: Hashable {
-    /**
-      `~=` compares two platforms to check if **lhs** platform images are compatible with **rhs** platform
-      This operator can be used to check if an image of **lhs** platform can run on **rhs**:
-      - `true`:  when **rhs**=`arm/v8`, **lhs** is any of `arm/v8`, `arm/v7`, `arm/v6` and `arm/v5`
-      - `true`:  when **rhs**=`arm/v7`, **lhs** is any of `arm/v7`, `arm/v6` and `arm/v5`
-      - `true`:  when **rhs**=`arm/v6`, **lhs** is any of `arm/v6` and `arm/v5`
-      - `true`:  when **rhs**=`amd64`, **lhs** is any of `amd64` and `386`
-      - `true`:  when **rhs**=**lhs**
-      - `false`:  otherwise
-      - Parameters:
-         - lhs: platform whose compatibility is being checked
-         - rhs: platform against which compatibility is being checked
-      - Returns: `true | false`
-     */
+    ///  `~=` compares two platforms to check if **lhs** platform images are compatible with **rhs** platform
+    ///  This operator can be used to check if an image of **lhs** platform can run on **rhs**:
+    ///  - `true`:  when **rhs**=`arm/v8`, **lhs** is any of `arm/v8`, `arm/v7`, `arm/v6` and `arm/v5`
+    ///  - `true`:  when **rhs**=`arm/v7`, **lhs** is any of `arm/v7`, `arm/v6` and `arm/v5`
+    ///  - `true`:  when **rhs**=`arm/v6`, **lhs** is any of `arm/v6` and `arm/v5`
+    ///  - `true`:  when **rhs**=`amd64`, **lhs** is any of `amd64` and `386`
+    ///  - `true`:  when **rhs**=**lhs**
+    ///  - `false`:  otherwise
+    ///  - Parameters:
+    ///     - lhs: platform whose compatibility is being checked
+    ///     - rhs: platform against which compatibility is being checked
+    ///  - Returns: `true | false`
     public static func ~= (lhs: Platform, rhs: Platform) -> Bool {
         if lhs.os == rhs.os {
             if lhs._rawArch == rhs._rawArch {

scripts/pre-commit.fmt

@@ -0,0 +1,16 @@
+#! /bin/bash -e
+
+setup_error() {
+    echo failed to run: $1 1>&2
+    echo run '"make pre-commit"' and try again 1>&2
+    exit 1
+}
+
+if [ ! -z "${PRECOMMIT_NOFMT}" ] ; then
+    exit 0
+fi
+
+echo checking formatting and licenses 1>&2
+project_pathname=$(git rev-parse --show-toplevel)
+cd "${project_pathname}"
+make check