diff --git a/api/publish.go b/api/publish.go
index 72ab38ae..5d9a8744 100644
--- a/api/publish.go
+++ b/api/publish.go
@@ -145,7 +145,7 @@ func apiPublishRepoOrSnapshot(c *gin.Context) {
 
 			sources = append(sources, snapshot)
 		}
-	} else if b.SourceKind == "local" {
+	} else if b.SourceKind == deb.SourceLocalRepo {
 		var localRepo *deb.LocalRepo
 
 		localCollection := context.CollectionFactory().LocalRepoCollection()
@@ -264,7 +264,7 @@ func apiPublishUpdateSwitch(c *gin.Context) {
 
 	var updatedComponents []string
 
-	if published.SourceKind == "local" {
+	if published.SourceKind == deb.SourceLocalRepo {
 		if len(b.Snapshots) > 0 {
 			c.Fail(400, fmt.Errorf("snapshots shouldn't be given when updating local repo"))
 			return
diff --git a/cmd/cmd.go b/cmd/cmd.go
index 35192d45..8ce39df8 100644
--- a/cmd/cmd.go
+++ b/cmd/cmd.go
@@ -14,6 +14,12 @@ import (
 	"github.com/smira/flag"
 )
 
+// Various command flags/UI things
+const (
+	Yes = "yes"
+	No  = "no"
+)
+
 // ListPackagesRefList shows list of packages in PackageRefList
 func ListPackagesRefList(reflist *deb.PackageRefList) (err error) {
 	fmt.Printf("Packages:\n")
diff --git a/cmd/db_cleanup.go b/cmd/db_cleanup.go
index 6833a049..9708641d 100644
--- a/cmd/db_cleanup.go
+++ b/cmd/db_cleanup.go
@@ -125,7 +125,7 @@ func aptlyDbCleanup(cmd *commander.Command, args []string) error {
 		if verbose {
 			context.Progress().ColoredPrintf("- @{g}%s:%s/%s{|}", published.Storage, published.Prefix, published.Distribution)
 		}
-		if published.SourceKind != "local" {
+		if published.SourceKind != deb.SourceLocalRepo {
 			return nil
 		}
 		e := context.CollectionFactory().PublishedRepoCollection().LoadComplete(published, context.CollectionFactory())
diff --git a/cmd/mirror_show.go b/cmd/mirror_show.go
index af94e742..73b829be 100644
--- a/cmd/mirror_show.go
+++ b/cmd/mirror_show.go
@@ -37,21 +37,21 @@ func aptlyMirrorShow(cmd *commander.Command, args []string) error {
 	fmt.Printf("Distribution: %s\n", repo.Distribution)
 	fmt.Printf("Components: %s\n", strings.Join(repo.Components, ", "))
 	fmt.Printf("Architectures: %s\n", strings.Join(repo.Architectures, ", "))
-	downloadSources := "no"
+	downloadSources := No
 	if repo.DownloadSources {
-		downloadSources = "yes"
+		downloadSources = Yes
 	}
 	fmt.Printf("Download Sources: %s\n", downloadSources)
-	downloadUdebs := "no"
+	downloadUdebs := No
 	if repo.DownloadUdebs {
-		downloadUdebs = "yes"
+		downloadUdebs = Yes
 	}
 	fmt.Printf("Download .udebs: %s\n", downloadUdebs)
 	if repo.Filter != "" {
 		fmt.Printf("Filter: %s\n", repo.Filter)
-		filterWithDeps := "no"
+		filterWithDeps := No
 		if repo.FilterWithDeps {
-			filterWithDeps = "yes"
+			filterWithDeps = Yes
 		}
 		fmt.Printf("Filter With Deps: %s\n", filterWithDeps)
 	}
diff --git a/cmd/publish_show.go b/cmd/publish_show.go
index 20355f95..e129e04d 100644
--- a/cmd/publish_show.go
+++ b/cmd/publish_show.go
@@ -41,13 +41,13 @@ func aptlyPublishShow(cmd *commander.Command, args []string) error {
 	fmt.Printf("Sources:\n")
 	for component, sourceID := range repo.Sources {
 		var name string
-		if repo.SourceKind == "snapshot" {
+		if repo.SourceKind == deb.SourceSnapshot {
 			source, e := context.CollectionFactory().SnapshotCollection().ByUUID(sourceID)
 			if e != nil {
 				continue
 			}
 			name = source.Name
-		} else if repo.SourceKind == "local" {
+		} else if repo.SourceKind == deb.SourceLocalRepo {
 			source, e := context.CollectionFactory().LocalRepoCollection().ByUUID(sourceID)
 			if e != nil {
 				continue
diff --git a/cmd/publish_snapshot.go b/cmd/publish_snapshot.go
index 9349811e..79a20007 100644
--- a/cmd/publish_snapshot.go
+++ b/cmd/publish_snapshot.go
@@ -35,7 +35,7 @@ func aptlyPublishSnapshotOrRepo(cmd *commander.Command, args []string) error {
 		message string
 	)
 
-	if cmd.Name() == "snapshot" {
+	if cmd.Name() == "snapshot" { // nolint: goconst
 		var (
 			snapshot     *deb.Snapshot
 			emptyWarning = false
@@ -71,7 +71,7 @@ func aptlyPublishSnapshotOrRepo(cmd *commander.Command, args []string) error {
 		if emptyWarning {
 			context.Progress().Printf("Warning: publishing from empty source, architectures list should be complete, it can't be changed after publishing (use -architectures flag)\n")
 		}
-	} else if cmd.Name() == "repo" {
+	} else if cmd.Name() == "repo" { // nolint: goconst
 		var (
 			localRepo    *deb.LocalRepo
 			emptyWarning = false
@@ -170,7 +170,7 @@ func aptlyPublishSnapshotOrRepo(cmd *commander.Command, args []string) error {
 
 	context.Progress().Printf("Now you can add following line to apt sources:\n")
 	context.Progress().Printf("  deb http://your-server/%s %s %s\n", prefix, distribution, repoComponents)
-	if utils.StrSliceHasItem(published.Architectures, "source") {
+	if utils.StrSliceHasItem(published.Architectures, deb.ArchitectureSource) {
 		context.Progress().Printf("  deb-src http://your-server/%s %s %s\n", prefix, distribution, repoComponents)
 	}
 	context.Progress().Printf("Don't forget to add your GPG key to apt with apt-key.\n")
diff --git a/cmd/publish_switch.go b/cmd/publish_switch.go
index 7c544ba8..86c3f2a8 100644
--- a/cmd/publish_switch.go
+++ b/cmd/publish_switch.go
@@ -44,7 +44,7 @@ func aptlyPublishSwitch(cmd *commander.Command, args []string) error {
 		return fmt.Errorf("unable to update: %s", err)
 	}
 
-	if published.SourceKind != "snapshot" {
+	if published.SourceKind != deb.SourceSnapshot {
 		return fmt.Errorf("unable to update: not a snapshot publish")
 	}
 
diff --git a/cmd/publish_update.go b/cmd/publish_update.go
index 7db3a3fe..587a6399 100644
--- a/cmd/publish_update.go
+++ b/cmd/publish_update.go
@@ -30,7 +30,7 @@ func aptlyPublishUpdate(cmd *commander.Command, args []string) error {
 		return fmt.Errorf("unable to update: %s", err)
 	}
 
-	if published.SourceKind != "local" {
+	if published.SourceKind != deb.SourceLocalRepo {
 		return fmt.Errorf("unable to update: not a local repository publish")
 	}
 
diff --git a/cmd/repo_create.go b/cmd/repo_create.go
index 9074a8f6..e63fed88 100644
--- a/cmd/repo_create.go
+++ b/cmd/repo_create.go
@@ -10,7 +10,7 @@ import (
 
 func aptlyRepoCreate(cmd *commander.Command, args []string) error {
 	var err error
-	if !(len(args) == 1 || (len(args) == 4 && args[1] == "from" && args[2] == "snapshot")) {
+	if !(len(args) == 1 || (len(args) == 4 && args[1] == "from" && args[2] == "snapshot")) { // nolint: goconst
 		cmd.Usage()
 		return commander.ErrCommandError
 	}
diff --git a/cmd/repo_move.go b/cmd/repo_move.go
index cff6af75..271ff039 100644
--- a/cmd/repo_move.go
+++ b/cmd/repo_move.go
@@ -34,7 +34,7 @@ func aptlyRepoMoveCopyImport(cmd *commander.Command, args []string) error {
 		srcRepo    *deb.LocalRepo
 	)
 
-	if command == "copy" || command == "move" {
+	if command == "copy" || command == "move" { // nolint: goconst
 		srcRepo, err = context.CollectionFactory().LocalRepoCollection().ByName(args[0])
 		if err != nil {
 			return fmt.Errorf("unable to %s: %s", command, err)
@@ -50,7 +50,7 @@ func aptlyRepoMoveCopyImport(cmd *commander.Command, args []string) error {
 		}
 
 		srcRefList = srcRepo.RefList()
-	} else if command == "import" {
+	} else if command == "import" { // nolint: goconst
 		var srcRemoteRepo *deb.RemoteRepo
 
 		srcRemoteRepo, err = context.CollectionFactory().RemoteRepoCollection().ByName(args[0])
@@ -122,11 +122,11 @@ func aptlyRepoMoveCopyImport(cmd *commander.Command, args []string) error {
 
 	var verb string
 
-	if command == "move" {
+	if command == "move" { // nolint: goconst
 		verb = "moved"
-	} else if command == "copy" {
+	} else if command == "copy" { // nolint: goconst
 		verb = "copied"
-	} else if command == "import" {
+	} else if command == "import" { // nolint: goconst
 		verb = "imported"
 	}
 
@@ -136,7 +136,7 @@ func aptlyRepoMoveCopyImport(cmd *commander.Command, args []string) error {
 			return err
 		}
 
-		if command == "move" {
+		if command == "move" { // nolint: goconst
 			srcList.Remove(p)
 		}
 		context.Progress().ColoredPrintf("@g[o]@| %s %s", p, verb)
@@ -156,7 +156,7 @@ func aptlyRepoMoveCopyImport(cmd *commander.Command, args []string) error {
 			return fmt.Errorf("unable to save: %s", err)
 		}
 
-		if command == "move" {
+		if command == "move" { // nolint: goconst
 			srcRepo.UpdateRefList(deb.NewPackageRefListFromPackageList(srcList))
 
 			err = context.CollectionFactory().LocalRepoCollection().Update(srcRepo)
diff --git a/cmd/serve.go b/cmd/serve.go
index 8bfb67c1..109335c9 100644
--- a/cmd/serve.go
+++ b/cmd/serve.go
@@ -90,7 +90,7 @@ func aptlyServe(cmd *commander.Command, args []string) error {
 		fmt.Printf("# %s\ndeb http://%s:%s/%s %s %s\n",
 			repo, listenHost, listenPort, prefix, repo.Distribution, strings.Join(repo.Components(), " "))
 
-		if utils.StrSliceHasItem(repo.Architectures, "source") {
+		if utils.StrSliceHasItem(repo.Architectures, deb.ArchitectureSource) {
 			fmt.Printf("deb-src http://%s:%s/%s %s %s\n",
 				listenHost, listenPort, prefix, repo.Distribution, strings.Join(repo.Components(), " "))
 		}
diff --git a/cmd/snapshot_create.go b/cmd/snapshot_create.go
index a9dcbe87..211e1e8b 100644
--- a/cmd/snapshot_create.go
+++ b/cmd/snapshot_create.go
@@ -13,7 +13,7 @@ func aptlySnapshotCreate(cmd *commander.Command, args []string) error {
 		snapshot *deb.Snapshot
 	)
 
-	if len(args) == 4 && args[1] == "from" && args[2] == "mirror" {
+	if len(args) == 4 && args[1] == "from" && args[2] == "mirror" { // nolint: goconst
 		// aptly snapshot create snap from mirror mirror
 		var repo *deb.RemoteRepo
 
@@ -38,7 +38,7 @@ func aptlySnapshotCreate(cmd *commander.Command, args []string) error {
 		if err != nil {
 			return fmt.Errorf("unable to create snapshot: %s", err)
 		}
-	} else if len(args) == 4 && args[1] == "from" && args[2] == "repo" {
+	} else if len(args) == 4 && args[1] == "from" && args[2] == "repo" { // nolint: goconst
 		// aptly snapshot create snap from repo repo
 		var repo *deb.LocalRepo
 
diff --git a/cmd/snapshot_search.go b/cmd/snapshot_search.go
index 875bcdb3..81413e07 100644
--- a/cmd/snapshot_search.go
+++ b/cmd/snapshot_search.go
@@ -26,7 +26,7 @@ func aptlySnapshotMirrorRepoSearch(cmd *commander.Command, args []string) error
 
 	var reflist *deb.PackageRefList
 
-	if command == "snapshot" {
+	if command == "snapshot" { // nolint: goconst
 		var snapshot *deb.Snapshot
 		snapshot, err = context.CollectionFactory().SnapshotCollection().ByName(name)
 		if err != nil {
@@ -52,7 +52,7 @@ func aptlySnapshotMirrorRepoSearch(cmd *commander.Command, args []string) error
 		}
 
 		reflist = repo.RefList()
-	} else if command == "repo" {
+	} else if command == "repo" { // nolint: goconst
 		var repo *deb.LocalRepo
 		repo, err = context.CollectionFactory().LocalRepoCollection().ByName(name)
 		if err != nil {
diff --git a/cmd/snapshot_show.go b/cmd/snapshot_show.go
index 03d8a5a6..e788f155 100644
--- a/cmd/snapshot_show.go
+++ b/cmd/snapshot_show.go
@@ -35,21 +35,21 @@ func aptlySnapshotShow(cmd *commander.Command, args []string) error {
 		fmt.Printf("Sources:\n")
 		for _, sourceID := range snapshot.SourceIDs {
 			var name string
-			if snapshot.SourceKind == "snapshot" {
+			if snapshot.SourceKind == deb.SourceSnapshot {
 				var source *deb.Snapshot
 				source, err = context.CollectionFactory().SnapshotCollection().ByUUID(sourceID)
 				if err != nil {
 					continue
 				}
 				name = source.Name
-			} else if snapshot.SourceKind == "local" {
+			} else if snapshot.SourceKind == deb.SourceLocalRepo {
 				var source *deb.LocalRepo
 				source, err = context.CollectionFactory().LocalRepoCollection().ByUUID(sourceID)
 				if err != nil {
 					continue
 				}
 				name = source.Name
-			} else if snapshot.SourceKind == "repo" {
+			} else if snapshot.SourceKind == deb.SourceRemoteRepo {
 				var source *deb.RemoteRepo
 				source, err = context.CollectionFactory().RemoteRepoCollection().ByUUID(sourceID)
 				if err != nil {
diff --git a/deb/changes.go b/deb/changes.go
index 7e975587..b3d4ca8a 100644
--- a/deb/changes.go
+++ b/deb/changes.go
@@ -170,7 +170,7 @@ func (c *Changes) PackageQuery() (PackageQuery, error) {
 
 	// if c.Source is empty, this would never match
 	sourceQuery := &AndQuery{
-		L: &FieldQuery{Field: "$PackageType", Relation: VersionEqual, Value: "source"},
+		L: &FieldQuery{Field: "$PackageType", Relation: VersionEqual, Value: ArchitectureSource},
 		R: &FieldQuery{Field: "Name", Relation: VersionEqual, Value: c.Source},
 	}
 
@@ -202,7 +202,7 @@ func (c *Changes) PackageQuery() (PackageQuery, error) {
 		}
 
 		binaryQuery = &AndQuery{
-			L: &NotQuery{Q: &FieldQuery{Field: "$PackageType", Relation: VersionEqual, Value: "source"}},
+			L: &NotQuery{Q: &FieldQuery{Field: "$PackageType", Relation: VersionEqual, Value: ArchitectureSource}},
 			R: binaryQuery}
 	}
 
diff --git a/deb/deb.go b/deb/deb.go
index ab720923..c98c9ad0 100644
--- a/deb/deb.go
+++ b/deb/deb.go
@@ -14,12 +14,18 @@ import (
 	"github.com/mkrautz/goar"
 	"github.com/pkg/errors"
 
-	"github.com/smira/aptly/aptly"
 	"github.com/smira/aptly/utils"
 	"github.com/smira/go-xz"
 	"github.com/smira/lzma"
 )
 
+// Source kinds
+const (
+	SourceSnapshot   = "snapshot"
+	SourceLocalRepo  = "local"
+	SourceRemoteRepo = "repo"
+)
+
 // GetControlFileFromDeb reads control file from deb package
 func GetControlFileFromDeb(packageFile string) (Stanza, error) {
 	file, err := os.Open(packageFile)
@@ -107,7 +113,7 @@ func GetControlFileFromDsc(dscFile string, verifier utils.Verifier) (Stanza, err
 }
 
 // GetContentsFromDeb returns list of files installed by .deb package
-func GetContentsFromDeb(file aptly.ReadSeekerCloser, packageFile string) ([]string, error) {
+func GetContentsFromDeb(file io.Reader, packageFile string) ([]string, error) {
 	library := ar.NewReader(file)
 	for {
 		header, err := library.Next()
diff --git a/deb/graph.go b/deb/graph.go
index b5b6947e..4c45ca9f 100644
--- a/deb/graph.go
+++ b/deb/graph.go
@@ -87,7 +87,7 @@ func BuildGraph(collectionFactory *CollectionFactory, layout string) (gographviz
 		}
 
 		description := snapshot.Description
-		if snapshot.SourceKind == "repo" {
+		if snapshot.SourceKind == SourceRemoteRepo {
 			description = "Snapshot from repo"
 		}
 
@@ -99,7 +99,7 @@ func BuildGraph(collectionFactory *CollectionFactory, layout string) (gographviz
 				snapshot.Name, description, snapshot.NumPackages(), labelEnd),
 		})
 
-		if snapshot.SourceKind == "repo" || snapshot.SourceKind == "local" || snapshot.SourceKind == "snapshot" {
+		if snapshot.SourceKind == SourceRemoteRepo || snapshot.SourceKind == SourceLocalRepo || snapshot.SourceKind == SourceSnapshot {
 			for _, uuid := range snapshot.SourceIDs {
 				_, exists := existingNodes[uuid]
 				if exists {
diff --git a/deb/index_files.go b/deb/index_files.go
index 0ea14897..9c860408 100644
--- a/deb/index_files.go
+++ b/deb/index_files.go
@@ -155,7 +155,7 @@ func newIndexFiles(publishedStorage aptly.PublishedStorage, basePath, tempDir, s
 }
 
 func (files *indexFiles) PackageIndex(component, arch string, udeb bool) *indexFile {
-	if arch == "source" {
+	if arch == ArchitectureSource {
 		udeb = false
 	}
 	key := fmt.Sprintf("pi-%s-%s-%v", component, arch, udeb)
@@ -163,7 +163,7 @@ func (files *indexFiles) PackageIndex(component, arch string, udeb bool) *indexF
 	if !ok {
 		var relativePath string
 
-		if arch == "source" {
+		if arch == ArchitectureSource {
 			relativePath = filepath.Join(component, "source", "Sources")
 		} else {
 			if udeb {
@@ -188,7 +188,7 @@ func (files *indexFiles) PackageIndex(component, arch string, udeb bool) *indexF
 }
 
 func (files *indexFiles) ReleaseIndex(component, arch string, udeb bool) *indexFile {
-	if arch == "source" {
+	if arch == ArchitectureSource {
 		udeb = false
 	}
 	key := fmt.Sprintf("ri-%s-%s-%v", component, arch, udeb)
@@ -196,7 +196,7 @@ func (files *indexFiles) ReleaseIndex(component, arch string, udeb bool) *indexF
 	if !ok {
 		var relativePath string
 
-		if arch == "source" {
+		if arch == ArchitectureSource {
 			relativePath = filepath.Join(component, "source", "Release")
 		} else {
 			if udeb {
@@ -221,7 +221,7 @@ func (files *indexFiles) ReleaseIndex(component, arch string, udeb bool) *indexF
 }
 
 func (files *indexFiles) ContentsIndex(component, arch string, udeb bool) *indexFile {
-	if arch == "source" {
+	if arch == ArchitectureSource {
 		udeb = false
 	}
 	key := fmt.Sprintf("ci-%s-%s-%v", component, arch, udeb)
diff --git a/deb/list.go b/deb/list.go
index b65c2826..e1942983 100644
--- a/deb/list.go
+++ b/deb/list.go
@@ -238,7 +238,7 @@ func (l *PackageList) Remove(p *Package) {
 func (l *PackageList) Architectures(includeSource bool) (result []string) {
 	result = make([]string, 0, 10)
 	for _, pkg := range l.packages {
-		if pkg.Architecture != "all" && (pkg.Architecture != "source" || includeSource) && !utils.StrSliceHasItem(result, pkg.Architecture) {
+		if pkg.Architecture != ArchitectureAll && (pkg.Architecture != ArchitectureSource || includeSource) && !utils.StrSliceHasItem(result, pkg.Architecture) {
 			result = append(result, pkg.Architecture)
 		}
 	}
diff --git a/deb/package.go b/deb/package.go
index d434bfbb..099e1551 100644
--- a/deb/package.go
+++ b/deb/package.go
@@ -41,6 +41,20 @@ type Package struct {
 	collection *PackageCollection
 }
 
+// Package types
+const (
+	PackageTypeBinary = "deb"
+	PackageTypeUdeb   = "udeb"
+	PackageTypeSource = "source"
+)
+
+// Special arhictectures
+const (
+	ArchitectureAll    = "all"
+	ArhictectureAny    = "any"
+	ArchitectureSource = "source"
+)
+
 // Check interface
 var (
 	_ json.Marshaler = &Package{}
@@ -218,12 +232,12 @@ func (p *Package) GetField(name string) string {
 		return p.Architecture
 	case "$PackageType":
 		if p.IsSource {
-			return "source"
+			return PackageTypeSource
 		}
 		if p.IsUdeb {
-			return "udeb"
+			return PackageTypeUdeb
 		}
-		return "deb"
+		return PackageTypeBinary
 	case "Name":
 		return p.Name
 	case "Version":
@@ -256,7 +270,7 @@ func (p *Package) GetField(name string) string {
 
 // MatchesArchitecture checks whether packages matches specified architecture
 func (p *Package) MatchesArchitecture(arch string) bool {
-	if p.Architecture == "all" && arch != "source" {
+	if p.Architecture == ArchitectureAll && arch != ArchitectureSource {
 		return true
 	}
 
diff --git a/deb/publish.go b/deb/publish.go
index afe0573d..15c7e990 100644
--- a/deb/publish.go
+++ b/deb/publish.go
@@ -96,19 +96,19 @@ func walkUpTree(source interface{}, collectionFactory *CollectionFactory) (rootD
 
 		if snapshot, ok := head.(*Snapshot); ok {
 			for _, uuid := range snapshot.SourceIDs {
-				if snapshot.SourceKind == "repo" {
+				if snapshot.SourceKind == SourceRemoteRepo {
 					remoteRepo, err := collectionFactory.RemoteRepoCollection().ByUUID(uuid)
 					if err != nil {
 						continue
 					}
 					current = append(current, remoteRepo)
-				} else if snapshot.SourceKind == "local" {
+				} else if snapshot.SourceKind == SourceLocalRepo {
 					localRepo, err := collectionFactory.LocalRepoCollection().ByUUID(uuid)
 					if err != nil {
 						continue
 					}
 					current = append(current, localRepo)
-				} else if snapshot.SourceKind == "snapshot" {
+				} else if snapshot.SourceKind == SourceSnapshot {
 					snap, err := collectionFactory.SnapshotCollection().ByUUID(uuid)
 					if err != nil {
 						continue
@@ -174,9 +174,9 @@ func NewPublishedRepo(storage, prefix, distribution string, architectures []stri
 	// figure out source kind
 	switch source.(type) {
 	case *Snapshot:
-		result.SourceKind = "snapshot"
+		result.SourceKind = SourceSnapshot
 	case *LocalRepo:
-		result.SourceKind = "local"
+		result.SourceKind = SourceLocalRepo
 	default:
 		panic("unknown source kind")
 	}
@@ -209,11 +209,11 @@ func NewPublishedRepo(storage, prefix, distribution string, architectures []stri
 			return nil, fmt.Errorf("duplicate component name: %s", component)
 		}
 
-		if result.SourceKind == "snapshot" {
+		if result.SourceKind == SourceSnapshot {
 			snapshot = source.(*Snapshot)
 			result.Sources[component] = snapshot.UUID
 			result.sourceItems[component] = repoSourceItem{snapshot: snapshot}
-		} else if result.SourceKind == "local" {
+		} else if result.SourceKind == SourceLocalRepo {
 			localRepo = source.(*LocalRepo)
 			result.Sources[component] = localRepo.UUID
 			result.sourceItems[component] = repoSourceItem{localRepo: localRepo, packageRefs: localRepo.RefList()}
@@ -349,10 +349,10 @@ func (p *PublishedRepo) RefKey(component string) []byte {
 // RefList returns list of package refs in local repo
 func (p *PublishedRepo) RefList(component string) *PackageRefList {
 	item := p.sourceItems[component]
-	if p.SourceKind == "local" {
+	if p.SourceKind == SourceLocalRepo {
 		return item.packageRefs
 	}
-	if p.SourceKind == "snapshot" {
+	if p.SourceKind == SourceSnapshot {
 		return item.snapshot.RefList()
 	}
 	panic("unknown source")
@@ -371,7 +371,7 @@ func (p *PublishedRepo) Components() []string {
 
 // UpdateLocalRepo updates content from local repo in component
 func (p *PublishedRepo) UpdateLocalRepo(component string) {
-	if p.SourceKind != "local" {
+	if p.SourceKind != SourceLocalRepo {
 		panic("not local repo publish")
 	}
 
@@ -384,7 +384,7 @@ func (p *PublishedRepo) UpdateLocalRepo(component string) {
 
 // UpdateSnapshot switches snapshot for component
 func (p *PublishedRepo) UpdateSnapshot(component string, snapshot *Snapshot) {
-	if p.SourceKind != "snapshot" {
+	if p.SourceKind != SourceSnapshot {
 		panic("not snapshot publish")
 	}
 
@@ -416,7 +416,7 @@ func (p *PublishedRepo) Decode(input []byte) error {
 
 	// old PublishedRepo were publishing only snapshots
 	if p.SourceKind == "" {
-		p.SourceKind = "snapshot"
+		p.SourceKind = SourceSnapshot
 	}
 
 	// <0.6 aptly used single SourceUUID + Component instead of Sources
@@ -677,7 +677,7 @@ func (p *PublishedRepo) Publish(packagePool aptly.PackagePool, publishedStorageP
 	release["Suite"] = p.Distribution
 	release["Codename"] = p.Distribution
 	release["Date"] = time.Now().UTC().Format("Mon, 2 Jan 2006 15:04:05 MST")
-	release["Architectures"] = strings.Join(utils.StrSlicesSubstract(p.Architectures, []string{"source"}), " ")
+	release["Architectures"] = strings.Join(utils.StrSlicesSubstract(p.Architectures, []string{ArchitectureSource}), " ")
 	release["Description"] = " Generated by aptly\n"
 	release["MD5Sum"] = ""
 	release["SHA1"] = ""
@@ -820,7 +820,7 @@ func (collection *PublishedRepoCollection) Update(repo *PublishedRepo) (err erro
 		return
 	}
 
-	if repo.SourceKind == "local" {
+	if repo.SourceKind == SourceLocalRepo {
 		for component, item := range repo.sourceItems {
 			err = collection.db.Put(repo.RefKey(component), item.packageRefs.Encode())
 			if err != nil {
@@ -835,7 +835,7 @@ func (collection *PublishedRepoCollection) Update(repo *PublishedRepo) (err erro
 func (collection *PublishedRepoCollection) LoadComplete(repo *PublishedRepo, collectionFactory *CollectionFactory) (err error) {
 	repo.sourceItems = make(map[string]repoSourceItem)
 
-	if repo.SourceKind == "snapshot" {
+	if repo.SourceKind == SourceSnapshot {
 		for component, sourceUUID := range repo.Sources {
 			item := repoSourceItem{}
 
@@ -850,7 +850,7 @@ func (collection *PublishedRepoCollection) LoadComplete(repo *PublishedRepo, col
 
 			repo.sourceItems[component] = item
 		}
-	} else if repo.SourceKind == "local" {
+	} else if repo.SourceKind == SourceLocalRepo {
 		for component, sourceUUID := range repo.Sources {
 			item := repoSourceItem{}
 
@@ -918,7 +918,7 @@ func (collection *PublishedRepoCollection) ByUUID(uuid string) (*PublishedRepo,
 func (collection *PublishedRepoCollection) BySnapshot(snapshot *Snapshot) []*PublishedRepo {
 	var result []*PublishedRepo
 	for _, r := range collection.list {
-		if r.SourceKind == "snapshot" {
+		if r.SourceKind == SourceSnapshot {
 			if r.SourceUUID == snapshot.UUID {
 				result = append(result, r)
 			}
@@ -938,7 +938,7 @@ func (collection *PublishedRepoCollection) BySnapshot(snapshot *Snapshot) []*Pub
 func (collection *PublishedRepoCollection) ByLocalRepo(repo *LocalRepo) []*PublishedRepo {
 	var result []*PublishedRepo
 	for _, r := range collection.list {
-		if r.SourceKind == "local" {
+		if r.SourceKind == SourceLocalRepo {
 			if r.SourceUUID == repo.UUID {
 				result = append(result, r)
 			}
diff --git a/deb/publish_test.go b/deb/publish_test.go
index b80fd6ec..ace1bce8 100644
--- a/deb/publish_test.go
+++ b/deb/publish_test.go
@@ -562,7 +562,7 @@ func (s *PublishedRepoCollectionSuite) TestLoadPre0_6(c *C) {
 		Prefix:        "ppa",
 		Distribution:  "anaconda",
 		Architectures: []string{"i386"},
-		SourceKind:    "local",
+		SourceKind:    SourceLocalRepo,
 		Component:     "contrib",
 		SourceUUID:    s.localRepo.UUID,
 	}
diff --git a/deb/remote.go b/deb/remote.go
index 4c739b21..ed87fa87 100644
--- a/deb/remote.go
+++ b/deb/remote.go
@@ -314,7 +314,7 @@ ok:
 		architectures := strings.Split(stanza["Architectures"], " ")
 		sort.Strings(architectures)
 		// "source" architecture is never present, despite Release file claims
-		architectures = utils.StrSlicesSubstract(architectures, []string{"source"})
+		architectures = utils.StrSlicesSubstract(architectures, []string{ArchitectureSource})
 		if len(repo.Architectures) == 0 {
 			repo.Architectures = architectures
 		} else if !repo.SkipArchitectureCheck {
@@ -410,20 +410,20 @@ func (repo *RemoteRepo) DownloadPackageIndexes(progress aptly.Progress, d aptly.
 	packagesURLs := [][]string{}
 
 	if repo.IsFlat() {
-		packagesURLs = append(packagesURLs, []string{repo.FlatBinaryURL().String(), "binary"})
+		packagesURLs = append(packagesURLs, []string{repo.FlatBinaryURL().String(), PackageTypeBinary})
 		if repo.DownloadSources {
-			packagesURLs = append(packagesURLs, []string{repo.FlatSourcesURL().String(), "source"})
+			packagesURLs = append(packagesURLs, []string{repo.FlatSourcesURL().String(), PackageTypeSource})
 		}
 	} else {
 		for _, component := range repo.Components {
 			for _, architecture := range repo.Architectures {
-				packagesURLs = append(packagesURLs, []string{repo.BinaryURL(component, architecture).String(), "binary"})
+				packagesURLs = append(packagesURLs, []string{repo.BinaryURL(component, architecture).String(), PackageTypeBinary})
 				if repo.DownloadUdebs {
-					packagesURLs = append(packagesURLs, []string{repo.UdebURL(component, architecture).String(), "udeb"})
+					packagesURLs = append(packagesURLs, []string{repo.UdebURL(component, architecture).String(), PackageTypeUdeb})
 				}
 			}
 			if repo.DownloadSources {
-				packagesURLs = append(packagesURLs, []string{repo.SourcesURL(component).String(), "source"})
+				packagesURLs = append(packagesURLs, []string{repo.SourcesURL(component).String(), PackageTypeSource})
 			}
 		}
 	}
@@ -455,11 +455,11 @@ func (repo *RemoteRepo) DownloadPackageIndexes(progress aptly.Progress, d aptly.
 
 			var p *Package
 
-			if kind == "binary" {
+			if kind == PackageTypeBinary {
 				p = NewPackageFromControlFile(stanza)
-			} else if kind == "udeb" {
+			} else if kind == PackageTypeUdeb {
 				p = NewUdebPackageFromControlFile(stanza)
-			} else if kind == "source" {
+			} else if kind == PackageTypeSource {
 				p, err = NewSourcePackageFromControlFile(stanza)
 				if err != nil {
 					return err
diff --git a/deb/snapshot.go b/deb/snapshot.go
index 2162f73f..59e298ba 100644
--- a/deb/snapshot.go
+++ b/deb/snapshot.go
@@ -44,7 +44,7 @@ func NewSnapshotFromRepository(name string, repo *RemoteRepo) (*Snapshot, error)
 		UUID:        uuid.New(),
 		Name:        name,
 		CreatedAt:   time.Now(),
-		SourceKind:  "repo",
+		SourceKind:  SourceRemoteRepo,
 		SourceIDs:   []string{repo.UUID},
 		Description: fmt.Sprintf("Snapshot from mirror %s", repo),
 		packageRefs: repo.packageRefs,
@@ -57,7 +57,7 @@ func NewSnapshotFromLocalRepo(name string, repo *LocalRepo) (*Snapshot, error) {
 		UUID:        uuid.New(),
 		Name:        name,
 		CreatedAt:   time.Now(),
-		SourceKind:  "local",
+		SourceKind:  SourceLocalRepo,
 		SourceIDs:   []string{repo.UUID},
 		Description: fmt.Sprintf("Snapshot from local repo %s", repo),
 		packageRefs: repo.packageRefs,
@@ -257,7 +257,7 @@ func (collection *SnapshotCollection) ByRemoteRepoSource(repo *RemoteRepo) []*Sn
 	var result []*Snapshot
 
 	for _, s := range collection.list {
-		if s.SourceKind == "repo" && utils.StrSliceHasItem(s.SourceIDs, repo.UUID) {
+		if s.SourceKind == SourceRemoteRepo && utils.StrSliceHasItem(s.SourceIDs, repo.UUID) {
 			result = append(result, s)
 		}
 	}
@@ -269,7 +269,7 @@ func (collection *SnapshotCollection) ByLocalRepoSource(repo *LocalRepo) []*Snap
 	var result []*Snapshot
 
 	for _, s := range collection.list {
-		if s.SourceKind == "local" && utils.StrSliceHasItem(s.SourceIDs, repo.UUID) {
+		if s.SourceKind == SourceLocalRepo && utils.StrSliceHasItem(s.SourceIDs, repo.UUID) {
 			result = append(result, s)
 		}
 	}
diff --git a/deb/snapshot_test.go b/deb/snapshot_test.go
index eb29855b..63890dcd 100644
--- a/deb/snapshot_test.go
+++ b/deb/snapshot_test.go
@@ -26,7 +26,7 @@ func (s *SnapshotSuite) TestNewSnapshotFromRepository(c *C) {
 	c.Check(snapshot.Name, Equals, "snap1")
 	c.Check(snapshot.NumPackages(), Equals, 3)
 	c.Check(snapshot.RefList().Len(), Equals, 3)
-	c.Check(snapshot.SourceKind, Equals, "repo")
+	c.Check(snapshot.SourceKind, Equals, SourceRemoteRepo)
 	c.Check(snapshot.SourceIDs, DeepEquals, []string{s.repo.UUID})
 
 	s.repo.packageRefs = nil
diff --git a/linter.json b/linter.json
index bbab4e46..37a32567 100644
--- a/linter.json
+++ b/linter.json
@@ -13,7 +13,9 @@
         "varcheck",
         "structcheck",
         "aligncheck",
-        "vetshadow"
+        "vetshadow",
+        "goconst",
+        "interfacer"
     ],
     "Deadline": "20m",
     "Vendor": true,