move FileExists to internal package

Signed-off-by: Samsondeen Dare <samsondeen.dare@hashicorp.com>

cmd/cosign/cli/generate/generate_key_pair.go

@@ -18,16 +18,17 @@ package generate
 import (
 	"context"
 	"crypto"
-	"errors"
 	"fmt"
 	"io"
 	"os"
 	"strings"
 
+	"github.com/pkg/errors"
 	"github.com/sigstore/cosign/pkg/cosign/git"
 	"github.com/sigstore/cosign/pkg/cosign/git/github"
 	"github.com/sigstore/cosign/pkg/cosign/git/gitlab"
 
+	icos "github.com/sigstore/cosign/internal/pkg/cosign"
 	"github.com/sigstore/cosign/pkg/cosign"
 	"github.com/sigstore/cosign/pkg/cosign/kubernetes"
 	"github.com/sigstore/sigstore/pkg/cryptoutils"
@@ -85,9 +86,9 @@ func GenerateKeyPairCmd(ctx context.Context, kmsVal string, args []string) error
 		return err
 	}
 
-	fileExists, err := cosign.FileExists("cosign.key")
+	fileExists, err := icos.FileExists("cosign.key")
 	if err != nil {
-		return err
+		return errors.Wrap(err, "error checking if cosign.key exists")
 	}
 
 	if fileExists {

cmd/cosign/cli/importkeypair/import_key_pair.go

@@ -21,6 +21,8 @@ import (
 	"io"
 	"os"
 
+	"github.com/pkg/errors"
+	icos "github.com/sigstore/cosign/internal/pkg/cosign"
 	"github.com/sigstore/cosign/pkg/cosign"
 )
 
@@ -36,9 +38,9 @@ func ImportKeyPairCmd(ctx context.Context, keyVal string, args []string) error {
 		return err
 	}
 
-	fileExists, err := cosign.FileExists("import-cosign.key\000x")
+	fileExists, err := icos.FileExists("import-cosign.key")
 	if err != nil {
-		return err
+		return errors.Wrap(err, "error checking if import-cosign.key exists")
 	}
 
 	if fileExists {

internal/pkg/cosign/common.go

@@ -0,0 +1,28 @@
+// Copyright 2021 The Sigstore Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cosign
+
+import "os"
+
+func FileExists(filename string) (bool, error) {
+	info, err := os.Stat(filename)
+	if os.IsNotExist(err) {
+		return false, nil
+	}
+	if err != nil {
+		return false, err
+	}
+	return !info.IsDir(), nil
+}

pkg/cosign/common.go

@@ -26,18 +26,6 @@ import (
 	"golang.org/x/term"
 )
 
-// TODO(jason): Move this to an internal package.
-func FileExists(filename string) (bool, error) {
-	info, err := os.Stat(filename)
-	if os.IsNotExist(err) {
-		return false, nil
-	}
-	if err != nil {
-		return false, err
-	}
-	return !info.IsDir(), nil
-}
-
 // ConfirmPrompt prompts the user for confirmation for an action. Supports skipping
 // the confirmation prompt when skipConfirmation is set.
 // TODO(jason): Move this to an internal package.