containers.conf: add new compose_providers option

Specify one or more external providers for the compose command.  The
first found provider is used for execution. Can be an absolute path or a
(file) name. Relative names are invalid.  File names are evaluated via
$PATH look ups.

Signed-off-by: Valentin Rothberg <[email protected]>

docs/containers.conf.5.md

@@ -428,6 +428,14 @@ Enforce using docker.io for completing short names in Podman's compatibility
 REST API. Note that this will ignore unqualified-search-registries and
 short-name aliases defined in containers-registries.conf(5).
 
+**compose_providers**=[]
+
+Specify one or more external providers for the compose command.  The first
+found provider is used for execution. Can be an absolute path or a (file) name.
+Can be an absolute and relative path or a (file) name.
+
+The defaults vary across supported platforms (Linux, FreeBSD, Mac OS, Windows).
+
 **compose_warning_logs**=true
 
 Emit logs on each invocation of the compose command indicating that an external

pkg/config/config.go

@@ -266,6 +266,11 @@ type EngineConfig struct {
 	// in containers-registries.conf(5).
 	CompatAPIEnforceDockerHub bool `toml:"compat_api_enforce_docker_hub,omitempty"`
 
+	// ComposeProviders specifies one or more external providers for the
+	// compose command.  The first found provider is used for execution.
+	// Can be an absolute and relative path or a (file) name.
+	ComposeProviders []string `toml:"compose_providers,omitempty"`
+
 	// ComposeWarningLogs emits logs on each invocation of the compose
 	// command indicating that an external compose provider is being
 	// executed.

pkg/config/config_local_test.go

@@ -476,6 +476,18 @@ var _ = Describe("Config Local", func() {
 		gomega.Expect(config2.Engine.CompatAPIEnforceDockerHub).To(gomega.Equal(false))
 	})
 
+	It("ComposeProviders", func() {
+		// Given
+		config, err := NewConfig("")
+		gomega.Expect(err).To(gomega.BeNil())
+		gomega.Expect(config.Engine.ComposeProviders).To(gomega.Equal(getDefaultComposeProviders())) // no hard-coding to work on all paltforms
+		// When
+		config2, err := NewConfig("testdata/containers_default.conf")
+		// Then
+		gomega.Expect(err).To(gomega.BeNil())
+		gomega.Expect(config2.Engine.ComposeProviders).To(gomega.Equal([]string{"/some/thing/else", "/than/before"}))
+	})
+
 	It("ComposeWarningLogs", func() {
 		// Given
 		config, err := NewConfig("")

pkg/config/containers.conf

@@ -381,6 +381,11 @@ default_sysctls = [
 # short-name aliases defined in containers-registries.conf(5).
 #compat_api_enforce_docker_hub = true
 
+# Specify one or more external providers for the compose command.  The first
+# found provider is used for execution. Can be an absolute path or a (file) name.
+# Can be an absolute and relative path or a (file) name.
+#compose_providers=[]
+
 # Emit logs on each invocation of the compose command indicating that an
 # external compose provider is being executed.
 #compose_warning_logs = true

pkg/config/default.go

@@ -260,6 +260,7 @@ func defaultConfigFromMemory() (*EngineConfig, error) {
 	c.EventsLogFileMaxSize = eventsLogMaxSize(DefaultEventsLogSizeMax)
 
 	c.CompatAPIEnforceDockerHub = true
+	c.ComposeProviders = getDefaultComposeProviders() // may vary across supported platforms
 	c.ComposeWarningLogs = true
 
 	if path, ok := os.LookupEnv("CONTAINERS_STORAGE_CONF"); ok {

pkg/config/default_common.go

@@ -5,3 +5,12 @@ package config
 
 // DefaultInitPath is the default path to the container-init binary.
 var DefaultInitPath = "/usr/libexec/podman/catatonit"
+
+var defaultUnixComposeProviders = []string{
+	"docker-compose",
+	"$HOME/.docker/cli-plugins/docker-compose",
+	"/usr/local/lib/docker/cli-plugins/docker-compose",
+	"/usr/local/libexec/docker/cli-plugins/docker-compose",
+	"/usr/lib/docker/cli-plugins/docker-compose",
+	"/usr/libexec/docker/cli-plugins/docker-compose",
+}

pkg/config/default_darwin.go

@@ -20,3 +20,7 @@ func getDefaultMachineVolumes() []string {
 		"/var/folders:/var/folders",
 	}
 }
+
+func getDefaultComposeProviders() []string {
+	return append(defaultUnixComposeProviders, "/opt/homebrew/bin/docker-compose", "podman-compose")
+}

pkg/config/default_freebsd.go

@@ -26,3 +26,7 @@ func getLibpodTmpDir() string {
 func getDefaultMachineVolumes() []string {
 	return []string{"$HOME:$HOME"}
 }
+
+func getDefaultComposeProviders() []string {
+	return append(defaultUnixComposeProviders, "podman-compose")
+}

pkg/config/default_linux.go

@@ -74,3 +74,7 @@ func getLibpodTmpDir() string {
 func getDefaultMachineVolumes() []string {
 	return []string{"$HOME:$HOME"}
 }
+
+func getDefaultComposeProviders() []string {
+	return append(defaultUnixComposeProviders, "podman-compose")
+}

pkg/config/default_windows.go

@@ -49,3 +49,8 @@ func getLibpodTmpDir() string {
 func getDefaultMachineVolumes() []string {
 	return []string{}
 }
+
+func getDefaultComposeProviders() []string {
+	// Rely on os.LookPath to do the trick on Windows.
+	return []string{"docker-compose", "podman-compose"}
+}

pkg/config/testdata/containers_default.conf

@@ -162,6 +162,11 @@ conmon_path = [
 # short-name aliases defined in containers-registries.conf(5).
 compat_api_enforce_docker_hub = false
 
+# Specify one or more external providers for the compose command.  The first
+# found provider is used for execution. Can be an absolute path or a (file) name.
+# Can be an absolute and relative path or a (file) name.
+compose_providers=["/some/thing/else", "/than/before"]
+
 # Emit logs on each invocation of the compose command indicating that an
 # external compose provider is being executed.
 compose_warning_logs = false