Integrate SwiftFormat into the swiftly project dependencies (#158)

The SwiftFormat that is run in the CI is a very specific version
that is unlikely to be the one a dev has installed with homebrew
or discovered for themselves and built from source. Discovering
the version involves finding the magic in the lint.dockerfile.

SwiftPM provides a mechanism for bringing in product dependencies
so that you can simply run using the toolchain. The dependencies
can be specified using an exact match on a particular version.

Add the SwiftFormat dependency as a package dependency in swiftly
at the version that is currently used in the soundness CI checks.
Use the the swift command to invoke the 'swiftformat' product from
the dependency instead of manually git cloning and building it
manually in the dockerfile.

Provide a rationale for the dependency in the Package.swift for
anyone who is curious about it.

Package.resolved

@@ -1,4 +1,5 @@
 {
+  "originHash" : "942a1612e8d4b18479d16ed7518859be9ac852972e43afb2a08c65d1037a641f",
   "pins" : [
     {
       "identity" : "async-http-client",
@@ -152,7 +153,16 @@
         "revision" : "3b13e439a341bbbfe0f710c7d1be37221745ef1a",
         "version" : "0.6.1"
       }
+    },
+    {
+      "identity" : "swiftformat",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/nicklockwood/SwiftFormat",
+      "state" : {
+        "revision" : "c7ddb09c3381cff833106345721fc314dba49e20",
+        "version" : "0.49.18"
+      }
     }
   ],
-  "version" : 2
+  "version" : 3
 }

Package.swift

@@ -22,6 +22,8 @@ let package = Package(
         .package(url: "https://github.com/apple/swift-nio.git", from: "2.64.0"),
         .package(url: "https://github.com/apple/swift-tools-support-core.git", from: "0.6.1"),
         .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.3.0"),
+        // This dependency provides the correct version of the formatter so that you can run `swift run swiftformat Package.swift Plugins/ Sources/ Tests/`
+        .package(url: "https://github.com/nicklockwood/SwiftFormat", exact: "0.49.18"),
     ],
     targets: [
         .executableTarget(

docker/lint.dockerfile

@@ -5,14 +5,3 @@ RUN apt-get update && apt-get install -y locales locales-all
 ENV LC_ALL en_US.UTF-8
 ENV LANG en_US.UTF-8
 ENV LANGUAGE en_US.UTF-8
-
-# tools
-RUN mkdir -p $HOME/.tools
-RUN echo 'export PATH="$HOME/.tools:$PATH"' >> $HOME/.profile
-
-# swiftformat (until part of the toolchain)
-
-ARG swiftformat_version=0.49.18
-RUN git clone --branch $swiftformat_version --depth 1 https://github.com/nicklockwood/SwiftFormat $HOME/.tools/swift-format
-RUN cd $HOME/.tools/swift-format && swift build -c release
-RUN ln -s $HOME/.tools/swift-format/.build/release/swiftformat $HOME/.tools/swiftformat

docker/test-amazonlinux2.dockerfile

@@ -15,7 +15,3 @@ COPY ./scripts/install-libarchive.sh /
 RUN /install-libarchive.sh
 
 RUN curl -L https://swift.org/keys/all-keys.asc | gpg --import
-
-# tools
-RUN mkdir -p $HOME/.tools
-RUN echo 'export PATH="$HOME/.tools:$PATH"' >> $HOME/.profile

docker/test-ubi9.dockerfile

@@ -15,7 +15,3 @@ COPY ./scripts/install-libarchive.sh /
 RUN /install-libarchive.sh
 
 RUN curl -L https://swift.org/keys/all-keys.asc | gpg --import
-
-# tools
-RUN mkdir -p $HOME/.tools
-RUN echo 'export PATH="$HOME/.tools:$PATH"' >> $HOME/.profile

docker/test.dockerfile

@@ -18,7 +18,3 @@ COPY ./scripts/install-libarchive.sh /
 RUN /install-libarchive.sh
 
 RUN curl -L https://swift.org/keys/all-keys.asc | gpg --import
-
-# tools
-RUN mkdir -p $HOME/.tools
-RUN echo 'export PATH="$HOME/.tools:$PATH"' >> $HOME/.profile

scripts/check-lint.sh

@@ -2,4 +2,4 @@
 
 set -o errexit
 
-swiftformat --lint --dryrun .
+swift run swiftformat --lint --dryrun .