importas: allow repeated aliases (#1960)

test/testdata/configs/importas.yml

@@ -1,5 +1,9 @@
 linters-settings:
   importas:
     alias:
-      fff: fmt
-      std_os: os
+      - pkg: fmt
+        alias: fff
+      - pkg: os
+        alias: std_os
+      - pkg: github.com/pkg/errors
+        alias: pkgerr

test/testdata/configs/importas_strict.yml

@@ -2,5 +2,9 @@ linters-settings:
   importas:
     no-unaliased: true
     alias:
-      fff: fmt
-      std_os: os
+      - pkg: fmt
+        alias: fff
+      - pkg: os
+        alias: std_os
+      - pkg: github.com/pkg/errors
+        alias: pkgerr

test/testdata/importas.go

@@ -6,10 +6,13 @@ import (
 	wrong_alias "fmt" // ERROR `import "fmt" imported as "wrong_alias" but must be "fff" according to config`
 	"os"
 	wrong_alias_again "os" // ERROR `import "os" imported as "wrong_alias_again" but must be "std_os" according to config`
+
+	wrong "github.com/pkg/errors" // ERROR `import "github.com/pkg/errors" imported as "wrong" but must be "pkgerr" according to config`
 )
 
 func ImportAsWrongAlias() {
 	wrong_alias.Println("foo")
 	wrong_alias_again.Stdout.WriteString("bar")
 	os.Stdout.WriteString("test")
+	_ = wrong.New("baz")
 }

test/testdata/importas_strict.go

@@ -6,10 +6,13 @@ import (
 	wrong_alias "fmt"      // ERROR `import "fmt" imported as "wrong_alias" but must be "fff" according to config`
 	"os"                   // ERROR `import "os" imported without alias but must be with alias "std_os" according to config`
 	wrong_alias_again "os" // ERROR `import "os" imported as "wrong_alias_again" but must be "std_os" according to config`
+
+	wrong "github.com/pkg/errors" // ERROR `import "github.com/pkg/errors" imported as "wrong" but must be "pkgerr" according to config`
 )
 
 func ImportAsStrictWrongAlias() {
 	wrong_alias.Println("foo")
 	wrong_alias_again.Stdout.WriteString("bar")
 	os.Stdout.WriteString("test")
+	_ = wrong.New("baz")
 }