pattern-based auto-split.

src/context.cr

@@ -142,6 +142,10 @@ class Package::Context
 			Package.new(recipe, true).tap do |split|
 				split.name = "#{recipe.name}-dev"
 				split.files = ["/usr/include"]
+				split.file_patterns = [
+					Regex.new("^/lib/.*\\.a$"),
+					Regex.new("^/usr/lib/.*\\.a$")
+				]
 			end
 		end
 	end

src/package.cr

@@ -31,6 +31,7 @@ class Package::Package
 
 	# Reference for splits. Recipe#packages[0] should keep this set to `nil`.
 	property files       : Array(String)?
+	property file_patterns : Array(Regex)?
 
 	def fake_root_directory
 		"#{@recipe.working_directory}/root-#{name}"

src/recipe.cr

@@ -15,6 +15,19 @@ class URI
 	end
 end
 
+module FileUtils
+	def self.find(directory, &block : Proc(String, Nil))
+		Dir.each_child directory do |child|
+			child_path = directory + "/" + child
+			yield child_path
+
+			if File.directory? child_path
+				self.find child_path, &block
+			end
+		end
+	end
+end
+
 class Package::Recipe
 	@context : Context
 
@@ -136,17 +149,29 @@ class Package::Recipe
 		(@packages + auto_splits).each do |package|
 			next if package == @packages[0]
 
-			files = package.files
+			files = package.files || [] of String
+			file_patterns = package.file_patterns || [] of Regex
 
-			next if files.nil? # Should only happen to @packages[0].
+			files_to_split = [] of String
-			# TODO: ↑ add public APIs that ensure it.
 
-			# FIXME: What do we do if those are not on the filesystem?
 			files.each do |file|
 				origin = "#{fake_root_directory}#{file}"
-				destination ="#{package.fake_root_directory}#{file}"
 
-				next unless File.exists? origin
+				if File.exists? origin
+					files_to_split << file
+				end
+			end
+
+			FileUtils.find fake_root_directory do |file|
+				file = file[fake_root_directory.size..file.size]
+				pp! file
+				files_to_split << file if file_patterns.any? &.match file
+			end
+
+			# FIXME: What do we do if those are not on the filesystem?
+			files_to_split.each do |file|
+				origin = "#{fake_root_directory}#{file}"
+				destination ="#{package.fake_root_directory}#{file}"
 
 				Dir.mkdir_p File.dirname destination