rootless: allow a per-user registries.conf file

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

docs/podman.1.md

@@ -155,6 +155,8 @@ Hooks are not used when running in rootless mode.
 
 registries.conf is the configuration file which specifies which container registries should be consulted when completing image names which do not include a registry or domain portion.
 
+When Podman runs in rootless mode, the file `$HOME/.config/containers/registries.conf` is used.
+
 ## Rootless mode
 Podman can also be used as non-root user.  When podman runs in rootless mode, an user namespace is automatically created.
 

pkg/registries/registries.go

@@ -2,15 +2,27 @@ package registries
 
 import (
 	"os"
+	"path/filepath"
 
 	"github.com/containers/image/pkg/sysregistries"
 	"github.com/containers/image/types"
 	"github.com/pkg/errors"
+	"github.com/projectatomic/libpod/pkg/rootless"
 )
 
+// userRegistriesFile is the path to the per user registry configuration file.
+var userRegistriesFile = filepath.Join(os.Getenv("HOME"), ".config/containers/registries.conf")
+
 // GetRegistries obtains the list of registries defined in the global registries file.
 func GetRegistries() ([]string, error) {
 	registryConfigPath := ""
+
+	if rootless.IsRootless() {
+		if _, err := os.Stat(userRegistriesFile); err == nil {
+			registryConfigPath = userRegistriesFile
+		}
+	}
+
 	envOverride := os.Getenv("REGISTRIES_CONFIG_PATH")
 	if len(envOverride) > 0 {
 		registryConfigPath = envOverride
@@ -25,6 +37,11 @@ func GetRegistries() ([]string, error) {
 // GetInsecureRegistries obtains the list of insecure registries from the global registration file.
 func GetInsecureRegistries() ([]string, error) {
 	registryConfigPath := ""
+
+	if _, err := os.Stat(userRegistriesFile); err == nil {
+		registryConfigPath = userRegistriesFile
+	}
+
 	envOverride := os.Getenv("REGISTRIES_CONFIG_PATH")
 	if len(envOverride) > 0 {
 		registryConfigPath = envOverride