apple-swift-format: linter and fixer with config swiftpm support (#3671)

doc/ale-swift.txt

@@ -2,6 +2,44 @@
 ALE Swift Integration                                       *ale-swift-options*
 
 
+===============================================================================
+apple-swift-format                               *ale-swift-apple-swift-format*
+
+There are 3 options to enable linting and fixing with Apple's swift-format:
+
+1. Install the local executable in your path, as described here:
+   https://github.com/apple/swift-format
+2. Install the executable via your OS package manager, for instance via
+   Homebrew with `brew install swift-format`
+3. Your Swift project has a dependency on the swift-format package, so it can
+   be run with `swift run swift-format lint ...` In this case, you need to set
+   a variable, see |g:ale_swift_appleswiftformat_use_swiftpm|.
+
+Additionally, ALE tries to locate and use the nearest existing `.swift-format`
+configuration file.
+
+
+g:ale_swift_appleswiftformat_executable *g:ale_swift_appleswiftformat_executable*
+                                      *b:ale_swift_appleswiftformat_executable*
+  Type: |String|
+  Default: `'swift-format'`
+
+  This variable can be modified to change the executable path for
+  `swift-format`.
+
+
+g:ale_swift_appleswiftformat_use_swiftpm *g:ale_swift_appleswiftformat_use_swiftpm*
+                                     *b:ale_swift_appleswiftformat_use_swiftpm*
+  Type: |Number|
+  Default: `0`
+
+  When set to `1`, this option will cause ALE to use
+  `swift run swift-format lint ...` instead of the global executable. Use this
+  option if your Swift project has a dependency on the swift-format package.
+
+  See |ale-integrations-local-executables|
+
+
 ===============================================================================
 sourcekitlsp                                           *ale-swift-sourcekitlsp*
 
@@ -16,6 +54,7 @@ g:ale_sourcekit_lsp_executable                 *g:ale_sourcekit_lsp_executable*
 
   See |ale-integrations-local-executables|
 
+
 ===============================================================================
   vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:
 

doc/ale.txt

@@ -3021,6 +3021,7 @@ documented in additional help files.
     prettier..............................|ale-svelte-prettier|
     svelteserver..........................|ale-svelte-svelteserver|
   swift...................................|ale-swift-options|
+    apple-swift-format....................|ale-swift-apple-swift-format|
     sourcekitlsp..........................|ale-swift-sourcekitlsp|
   systemd.................................|ale-systemd-options|
     systemd-analyze.......................|ale-systemd-analyze|