Add GitLab CI credentials helper

This simplifies usage of Kaniko in GitLab CI environments and
means that it's not longer necessary to manually cobble together
the config with the right values from the environment in
error-prone shell commands.

go.mod

@@ -93,6 +93,7 @@ require (
 	github.com/docker/go-metrics v0.0.1 // indirect
 	github.com/docker/go-units v0.4.0 // indirect
 	github.com/docker/swarmkit v1.12.1-0.20180726190244-7567d47988d8 // indirect
+	github.com/ePirat/docker-credential-gitlabci v1.0.0
 	github.com/emirpasic/gods v1.12.0 // indirect
 	github.com/fsnotify/fsnotify v1.5.1 // indirect
 	github.com/go-git/gcfg v1.5.0 // indirect

go.sum

@@ -604,6 +604,8 @@ github.com/docker/swarmkit v1.12.1-0.20180726190244-7567d47988d8/go.mod h1:n3Z4l
 github.com/docopt/docopt-go v0.0.0-20180111231733-ee0de3bc6815/go.mod h1:WwZ+bS3ebgob9U8Nd0kOddGdZWjyMGR8Wziv+TBNwSE=
 github.com/dustin/go-humanize v0.0.0-20171111073723-bb3d318650d4/go.mod h1:HtrtbFcZ19U5GC7JDqmcUSB87Iq5E25KnS6fMYU6eOk=
 github.com/dustin/go-humanize v1.0.0/go.mod h1:HtrtbFcZ19U5GC7JDqmcUSB87Iq5E25KnS6fMYU6eOk=
+github.com/ePirat/docker-credential-gitlabci v1.0.0 h1:YRkUSvkON6rT88vtscClAmPEYWhtltGEAuRVYtz1/+Y=
+github.com/ePirat/docker-credential-gitlabci v1.0.0/go.mod h1:Ptmh+D0lzBQtgb6+QHjXl9HqOn3T1P8fKUHldiSQQGA=
 github.com/eapache/go-resiliency v1.1.0/go.mod h1:kFI+JgMyC7bLPUVY133qvEBtVayf5mFgVsvEsIPBvNs=
 github.com/eapache/go-xerial-snappy v0.0.0-20180814174437-776d5712da21/go.mod h1:+020luEh2TKB4/GOp8oxxtq0Daoen/Cii55CzbTV6DU=
 github.com/eapache/queue v1.1.0/go.mod h1:6eCeP0CKFpHLu8blIFXhExK/dRa7WDZfr6jVFPTqq+I=

pkg/creds/creds.go

@@ -21,6 +21,7 @@ import (
 
 	ecr "github.com/awslabs/amazon-ecr-credential-helper/ecr-login"
 	"github.com/chrismellard/docker-credential-acr-env/pkg/credhelper"
+	gitlab "github.com/ePirat/docker-credential-gitlabci/pkg/credhelper"
 	"github.com/google/go-containerregistry/pkg/authn"
 	"github.com/google/go-containerregistry/pkg/v1/google"
 )
@@ -32,5 +33,6 @@ func GetKeychain() authn.Keychain {
 		google.Keychain,
 		authn.NewKeychainFromHelper(ecr.NewECRHelper(ecr.WithLogger(ioutil.Discard))),
 		authn.NewKeychainFromHelper(credhelper.NewACRCredentialsHelper()),
+		authn.NewKeychainFromHelper(gitlab.NewGitLabCredentialsHelper()),
 	)
 }

vendor/modules.txt

@@ -434,6 +434,9 @@ github.com/docker/swarmkit/log
 github.com/docker/swarmkit/manager/raftselector
 github.com/docker/swarmkit/protobuf/plugin
 github.com/docker/swarmkit/protobuf/ptypes
+# github.com/ePirat/docker-credential-gitlabci v1.0.0
+## explicit; go 1.17
+github.com/ePirat/docker-credential-gitlabci/pkg/credhelper
 # github.com/emirpasic/gods v1.12.0
 ## explicit
 github.com/emirpasic/gods/containers