Make archive priority int32

Archive priority is currently defined as int. This can make chisel.yaml
with very high/low priorities non-portable, e.g. from amd64 to arm32.

Change archive priority definition to int32 data type.

internal/archive/archive.go

@@ -34,7 +34,7 @@ type Options struct {
 	Suites     []string
 	Components []string
 	CacheDir   string
-	Priority   int
+	Priority   int32
 }
 
 func Open(options *Options) (Archive, error) {

internal/setup/setup.go

@@ -29,7 +29,7 @@ type Archive struct {
 	Version    string
 	Suites     []string
 	Components []string
-	Priority   int
+	Priority   int32
 }
 
 // Package holds a collection of slices that represent parts of themselves.
@@ -322,7 +322,7 @@ type yamlArchive struct {
 	Version    string   `yaml:"version"`
 	Suites     []string `yaml:"suites"`
 	Components []string `yaml:"components"`
-	Priority   int      `yaml:"priority"`
+	Priority   int32    `yaml:"priority"`
 }
 
 type yamlPackage struct {

internal/setup/setup_test.go

@@ -766,6 +766,30 @@ var setupTests = []setupTest{{
 			},
 		},
 	},
+}, {
+	summary: "Maximum priority",
+	input: map[string]string{
+		"chisel.yaml": `
+			format: chisel-v1
+			archives:
+				upper-limit:
+					version: 1
+					suites: [main]
+					components: [main]
+					priority: 2147483647
+				lower-limit:
+					version: 1
+					suites: [main]
+					components: [main]
+					priority: -2147483648
+				over-limit:
+					version: 1
+					suites: [main]
+					components: [main]
+					priority: 2147483648
+		`,
+	},
+	relerror: "(?s).*\\bcannot unmarshal !!int `2147483648` into int32\\b.*",
 }}
 
 const defaultChiselYaml = `

internal/slicer/slicer.go

@@ -72,8 +72,8 @@ func Run(options *RunOptions) error {
 	}
 
 	// Archives are ordered in descending order by priority. The
-	// default priority is 0 and the maximum allowed priority is
-	// the upper limit of int.
+	// default priority is 0 and the range of allowed priorities
+	// is the same as the range of the int32 data type.
 	//
 	// If a package to be downloaded exists in archive A and
 	// archive B, and archive A has higher priority than archive
@@ -111,7 +111,7 @@ func Run(options *RunOptions) error {
 		if extractPackage == nil {
 			var selectedVersion string
 			var selectedArchive archive.Archive
-			currentPrio := math.MaxInt
+			var currentPrio int32 = math.MaxInt32
 			for _, currentArchive := range orderedArchives {
 				if prio := currentArchive.Options().Priority; prio < currentPrio {
 					if selectedVersion != "" {