vendor c/{buildah,common}: appendable containers.conf strings, Part 1

This change is the first step of integrating appendable string arrays
into containers.conf and starts with enabling the `Env`, `Mounts`, and
`Volumes` fields in the `[Containers]` table.

Both, Buildah and Podman, read (and sometimes write) the fields of the
`Config` struct at various places, so I decided to migrate the fields
step-by-step.  The ones in this change are most critical ones for
customers.  Once all string slices/arrays are migrated, the docs of
containers.conf will be updated.  The current changes are entirely
transparent to users.

Signed-off-by: Valentin Rothberg <vrothberg@redhat.com>

vendor/github.com/containers/common/internal/attributedstring/slice.go

@@ -0,0 +1,92 @@
+package attributedstring
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/BurntSushi/toml"
+)
+
+// Slice allows for extending a TOML string array with custom
+// attributes that control how the array is marshaled into a Go string.
+//
+// Specifically, an Slice can be configured to avoid it being
+// overridden by a subsequent unmarshal sequence.  When the `append` attribute
+// is specified, the array will be appended instead (e.g., `array=["9",
+// {append=true}]`).
+type Slice struct { // A "mixed-type array" in TOML.
+	// Note that the fields below _must_ be exported.  Otherwise the TOML
+	// encoder would fail during type reflection.
+	Values     []string
+	Attributes struct { // Using a struct allows for adding more attributes in the future.
+		Append *bool // Nil if not set by the user
+	}
+}
+
+// Get returns the Slice values or an empty string slice.
+func (a *Slice) Get() []string {
+	if a.Values == nil {
+		return []string{}
+	}
+	return a.Values
+}
+
+// UnmarshalTOML is the custom unmarshal method for Slice.
+func (a *Slice) UnmarshalTOML(data interface{}) error {
+	iFaceSlice, ok := data.([]interface{})
+	if !ok {
+		return fmt.Errorf("unable to cast to interface array: %v", data)
+	}
+
+	var loadedStrings []string
+	for _, x := range iFaceSlice { // Iterate over each item in the slice.
+		switch val := x.(type) {
+		case string: // Strings are directly appended to the slice.
+			loadedStrings = append(loadedStrings, val)
+		case map[string]interface{}: // The attribute struct is represented as a map.
+			for k, v := range val { // Iterate over all _supported_ keys.
+				switch k {
+				case "append":
+					boolVal, ok := v.(bool)
+					if !ok {
+						return fmt.Errorf("unable to cast append to bool: %v", k)
+					}
+					a.Attributes.Append = &boolVal
+				default: // Unsupported map key.
+					return fmt.Errorf("unsupported key %q in map: %v", k, val)
+				}
+			}
+		default: // Unsupported item.
+			return fmt.Errorf("unsupported item in attributed string slice: %v", x)
+		}
+	}
+
+	if a.Attributes.Append != nil && *a.Attributes.Append { // If _explicitly_ configured, append the loaded slice.
+		a.Values = append(a.Values, loadedStrings...)
+	} else { // Default: override the existing Slice.
+		a.Values = loadedStrings
+	}
+	return nil
+}
+
+// MarshalTOML is the custom marshal method for Slice.
+func (a *Slice) MarshalTOML() ([]byte, error) {
+	iFaceSlice := make([]interface{}, 0, len(a.Values))
+
+	for _, x := range a.Values {
+		iFaceSlice = append(iFaceSlice, x)
+	}
+
+	if a.Attributes.Append != nil {
+		Attributes := make(map[string]any)
+		Attributes["append"] = *a.Attributes.Append
+		iFaceSlice = append(iFaceSlice, Attributes)
+	}
+
+	buf := new(bytes.Buffer)
+	enc := toml.NewEncoder(buf)
+	if err := enc.Encode(iFaceSlice); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}

vendor/github.com/containers/common/pkg/config/config.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"github.com/BurntSushi/toml"
+	"github.com/containers/common/internal/attributedstring"
 	"github.com/containers/common/libnetwork/types"
 	"github.com/containers/common/pkg/capabilities"
 	"github.com/containers/common/pkg/util"
@@ -71,7 +72,7 @@ type ContainersConfig struct {
 	Devices []string `toml:"devices,omitempty"`
 
 	// Volumes to add to all containers
-	Volumes []string `toml:"volumes,omitempty"`
+	Volumes attributedstring.Slice `toml:"volumes,omitempty"`
 
 	// ApparmorProfile is the apparmor profile name which is used as the
 	// default for the runtime.
@@ -133,7 +134,7 @@ type ContainersConfig struct {
 	EnableLabeledUsers bool `toml:"label_users,omitempty"`
 
 	// Env is the environment variable list for container process.
-	Env []string `toml:"env,omitempty"`
+	Env attributedstring.Slice `toml:"env,omitempty"`
 
 	// EnvHost Pass all host environment variables into the container.
 	EnvHost bool `toml:"env_host,omitempty"`
@@ -171,7 +172,7 @@ type ContainersConfig struct {
 	LogTag string `toml:"log_tag,omitempty"`
 
 	// Mount to add to all containers
-	Mounts []string `toml:"mounts,omitempty"`
+	Mounts attributedstring.Slice `toml:"mounts,omitempty"`
 
 	// NetNS indicates how to create a network namespace for the container
 	NetNS string `toml:"netns,omitempty"`
@@ -907,7 +908,7 @@ func (c *Config) GetDefaultEnvEx(envHost, httpProxy bool) []string {
 			}
 		}
 	}
-	return append(env, c.Containers.Env...)
+	return append(env, c.Containers.Env.Get()...)
 }
 
 // Capabilities returns the capabilities parses the Add and Drop capability

vendor/github.com/containers/common/pkg/config/default.go

@@ -9,6 +9,7 @@ import (
 	"runtime"
 	"strings"
 
+	"github.com/containers/common/internal/attributedstring"
 	nettypes "github.com/containers/common/libnetwork/types"
 	"github.com/containers/common/pkg/apparmor"
 	"github.com/containers/common/pkg/cgroupv2"
@@ -204,8 +205,8 @@ func defaultConfig() (*Config, error) {
 			Devices:             []string{},
 			EnableKeyring:       true,
 			EnableLabeling:      selinuxEnabled(),
-			Env: []string{
-				"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
+			Env: attributedstring.Slice{
+				Values: []string{"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"},
 			},
 			EnvHost:    false,
 			HTTPProxy:  true,
@@ -214,7 +215,7 @@ func defaultConfig() (*Config, error) {
 			InitPath:   "",
 			LogDriver:  defaultLogDriver(),
 			LogSizeMax: DefaultLogSizeMax,
-			Mounts:     []string{},
+			Mounts:     attributedstring.Slice{},
 			NetNS:      "private",
 			NoHosts:    false,
 			PidNS:      "private",
@@ -224,7 +225,7 @@ func defaultConfig() (*Config, error) {
 			UTSNS:      "private",
 			Umask:      "0022",
 			UserNSSize: DefaultUserNSSize, // Deprecated
-			Volumes:    []string{},
+			Volumes:    attributedstring.Slice{},
 		},
 		Network: NetworkConfig{
 			DefaultNetwork:            "podman",
@@ -509,12 +510,12 @@ func (c *Config) Sysctls() []string {
 
 // Volumes returns the default set of volumes that should be mounted in containers.
 func (c *Config) Volumes() []string {
-	return c.Containers.Volumes
+	return c.Containers.Volumes.Get()
 }
 
 // Mounts returns the default set of mounts that should be mounted in containers.
 func (c *Config) Mounts() []string {
-	return c.Containers.Mounts
+	return c.Containers.Mounts.Get()
 }
 
 // Devices returns the default additional devices for containers.
@@ -539,7 +540,7 @@ func (c *Config) DNSOptions() []string {
 
 // Env returns the default additional environment variables to add to containers.
 func (c *Config) Env() []string {
-	return c.Containers.Env
+	return c.Containers.Env.Values
 }
 
 // IPCNS returns the default IPC Namespace configuration to run containers with.