Add package mapping capability

If a given package/pattern in the source machine had been
renamed/splitted/removed in the target machine, we need a way to map
those packages/patterns into the new packages/patterns. This functionality
is expecially helpful for cross-OS migration (i.e. CentOS to openSUSE).

export_helpers/salt_package_map.sample

@@ -0,0 +1,37 @@
+# One-to-one package map. Source package version match is optional. If
+# specified, the version must match the source package version for the mapping
+# to take effect. If source package version is absent, that means it will
+# match any version. Likewise, target package version is optional.
+# When specified, it will map to a specific target package version. Otherwise,
+# it will map to the latest version.
+<source package name>:
+  version: <source package version match>
+  packages:
+    - name: <target package name>
+      version: <target package version>
+
+# Map a source pattern package.
+<source pattern package name>
+  version: <source pattern package version match>
+  pattern: yes
+  packages:
+    - name: <target pattern package name>
+      version: <target pattern package version>
+      pattern: yes
+
+# One-to-many map. A source package can map to multiple packages and/or
+# patterns. 
+<source package name>:
+  version: <source package version match>
+  packages:
+    - name: <target pattern package name>
+      version: <target pattern package version>
+      pattern: yes
+    - name: <target package name>
+      version: <target pacakge version>
+
+# A package without mapping means there are no target packages to map there.
+# Therefore, it will be excluded from migration.
+<source package name>:
+  version: <source package version match>
+

lib/salt_states.rb

@@ -37,12 +37,14 @@ def initialize(system_description, options)
       @system_description = system_description
       @options = options
       @group_id_to_name_mapping = {}
+      @package_map = nil
 
       @system_description.assert_scopes(
         "packages",
         "os"
       )
       check_existance_of_extracted_files
+      load_package_map
     end
 
     def write(output_location)
@@ -95,6 +97,15 @@ def check_existance_of_extracted_files
       end
     end
 
+    def load_package_map
+      package_map_file = File.join(
+        Machinery::ROOT, "export_helpers/#{@name}_package_map"
+      )
+      if File.file?(package_map_file)
+        @package_map = YAML.load_file(package_map_file)
+      end
+    end
+
     def add_group(name, gid)
       @group_id_to_name_mapping[gid] = name
       salt_group = <<~SALT
@@ -382,52 +393,81 @@ def managed_file_states(output_location)
       managed_files_sls
     end
 
-    def add_package(package)
+    def add_package(name, version, pattern)
       salt_package = <<~SALT
-        install-package-#{package.name}:
+        install-package-#{name}:
           pkg.installed:
-            - name: #{package.name}
+            - name: #{name}
       SALT
 
-      if @options["skip-package-version"]
+      if pattern
+        salt_package += "    - includes: [pattern]\n"
+      end
+
+      if @options["skip-package-version"] or version.nil?
         salt_package + "\n"
       else
-        salt_package + "    - version: '#{package.version}'\n\n"
+        salt_package + "    - version: '#{version}'\n\n"
       end
     end
 
-    def add_pattern(pattern)
-      <<~SALT
-        install-pattern-#{pattern.name}:
-          pkg.installed:
-            - name: pattern:#{pattern.name}
-            - version: '#{pattern.version}'
-            - includes: [pattern]
+    def package_pattern_match?(package_mapping, pattern)
+      pattern == package_mapping.fetch('pattern', false)
+    end
 
-      SALT
+    def package_version_match?(package_mapping, version)
+      !package_mapping.include?('version') or (
+      package_mapping['version'] == version)
+    end
+
+    def package_has_mapping?(name, version, pattern)
+      if @package_map and @package_map.include?(name)
+        if @package_map[name] and @package_map[name].is_a?(Hash)
+          return (package_pattern_match?(@package_map[name], pattern) and
+                  package_version_match?(@package_map[name], version))
+        else
+          return !pattern
+        end
+      else
+        return false
+      end
+    end
+
+    def map_package(name, version, pattern)
+      if package_has_mapping?(name, version, pattern)
+        if @package_map[name].is_a?(Hash) and
+           @package_map[name].include?('packages')
+          packages = []
+          @package_map[name]['packages'].each do |package|
+            packages.append([package['name'], package.fetch('version', nil),
+                             package.fetch('pattern', false)])
+          end
+          return packages
+        else
+          # package maps to nothing. This means the package will not be
+          # migrated.
+          return []
+        end
+      else
+        [[name, version, pattern]]
+      end
     end
 
     def package_states
-      uniq_packages = []
-      packages_sls = ""
+      packages = []
       @system_description&.packages&.each do |package|
-        # FIXME(gyee): seem like a bug in inspection that it has duplicate
-        # entries for packages in manifest.json.
-        next if uniq_packages.include? package.name
-
-        uniq_packages.push(package.name)
-        packages_sls += add_package(package)
+        packages += map_package(package.name, package.version, false)
+      end
+      @system_description&.patterns&.each do |package|
+        packages += map_package(package.name, package.version, true)
       end
-      uniq_patterns = []
-      @system_description&.patterns&.each do |pattern|
-        # FIXME(gyee): seem like a bug in inspection that it has duplicate
-        # entries for packages in manifest.json.
-        next if uniq_patterns.include? pattern.name
-
-        uniq_patterns.push(pattern.name)
-        packages_sls += add_pattern(pattern)
+
+      packages = packages.uniq
+      salt_package_states = ''
+      packages.each do |package|
+        salt_package_states += add_package(package[0], package[1], package[2])
       end
-      packages_sls
+      salt_package_states
     end
 
     def add_repo(repo)