feat(agent/agentcontainers): auto detect dev containers (#18950)

Relates to https://github.com/coder/internal/issues/711

This PR implements a project discovery mechanism that searches for any
dev container projects and makes them visible in the UI so that they can
be started. To make the wording on the site more clear, "Rebuild" has
been changed to "Start" when there is no container associated with a
known dev container configuration. I've also made it so that site will
show the dev container config path when there is no other name
available.

### Design decisions

Just want to ensure my explanation for a few design decisions are noted
down:
- We only search for dev container configurations inside git
repositories
- We only search for these git repositories if they're at the top level
or a direct child of the agent directory.

This limited approach is to reduce the amount of files we ultimately
walk when trying to find these projects. It makes sense to limit it to
only the agent directory, although I'm open to expanding how deep we
search.

cli/agent.go

@@ -40,22 +40,23 @@ import (
 
 func (r *RootCmd) workspaceAgent() *serpent.Command {
 	var (
-		auth                string
-		logDir              string
-		scriptDataDir       string
-		pprofAddress        string
-		noReap              bool
-		sshMaxTimeout       time.Duration
-		tailnetListenPort   int64
-		prometheusAddress   string
-		debugAddress        string
-		slogHumanPath       string
-		slogJSONPath        string
-		slogStackdriverPath string
-		blockFileTransfer   bool
-		agentHeaderCommand  string
-		agentHeader         []string
-		devcontainers       bool
+		auth                         string
+		logDir                       string
+		scriptDataDir                string
+		pprofAddress                 string
+		noReap                       bool
+		sshMaxTimeout                time.Duration
+		tailnetListenPort            int64
+		prometheusAddress            string
+		debugAddress                 string
+		slogHumanPath                string
+		slogJSONPath                 string
+		slogStackdriverPath          string
+		blockFileTransfer            bool
+		agentHeaderCommand           string
+		agentHeader                  []string
+		devcontainers                bool
+		devcontainerProjectDiscovery bool
 	)
 	cmd := &serpent.Command{
 		Use:   "agent",
@@ -364,6 +365,7 @@ func (r *RootCmd) workspaceAgent() *serpent.Command {
 					Devcontainers:      devcontainers,
 					DevcontainerAPIOptions: []agentcontainers.Option{
 						agentcontainers.WithSubAgentURL(r.agentURL.String()),
+						agentcontainers.WithProjectDiscovery(devcontainerProjectDiscovery),
 					},
 				})
 
@@ -510,6 +512,13 @@ func (r *RootCmd) workspaceAgent() *serpent.Command {
 			Description: "Allow the agent to automatically detect running devcontainers.",
 			Value:       serpent.BoolOf(&devcontainers),
 		},
+		{
+			Flag:        "devcontainers-project-discovery-enable",
+			Default:     "true",
+			Env:         "CODER_AGENT_DEVCONTAINERS_PROJECT_DISCOVERY_ENABLE",
+			Description: "Allow the agent to search the filesystem for devcontainer projects.",
+			Value:       serpent.BoolOf(&devcontainerProjectDiscovery),
+		},
 	}
 
 	return cmd

cli/exp_rpty_test.go

@@ -118,6 +118,7 @@ func TestExpRpty(t *testing.T) {
 		_ = agenttest.New(t, client.URL, agentToken, func(o *agent.Options) {
 			o.Devcontainers = true
 			o.DevcontainerAPIOptions = append(o.DevcontainerAPIOptions,
+				agentcontainers.WithProjectDiscovery(false),
 				agentcontainers.WithContainerLabelIncludeFilter(wantLabel, "true"),
 			)
 		})

cli/open_test.go

@@ -406,6 +406,7 @@ func TestOpenVSCodeDevContainer(t *testing.T) {
 	_ = agenttest.New(t, client.URL, agentToken, func(o *agent.Options) {
 		o.Devcontainers = true
 		o.DevcontainerAPIOptions = append(o.DevcontainerAPIOptions,
+			agentcontainers.WithProjectDiscovery(false),
 			agentcontainers.WithContainerCLI(fCCLI),
 			agentcontainers.WithDevcontainerCLI(fDCCLI),
 			agentcontainers.WithWatcher(watcher.NewNoop()),

cli/ssh_test.go

@@ -2031,6 +2031,7 @@ func TestSSH_Container(t *testing.T) {
 		_ = agenttest.New(t, client.URL, agentToken, func(o *agent.Options) {
 			o.Devcontainers = true
 			o.DevcontainerAPIOptions = append(o.DevcontainerAPIOptions,
+				agentcontainers.WithProjectDiscovery(false),
 				agentcontainers.WithContainerLabelIncludeFilter("this.label.does.not.exist.ignore.devcontainers", "true"),
 			)
 		})
@@ -2072,6 +2073,7 @@ func TestSSH_Container(t *testing.T) {
 			o.Devcontainers = true
 			o.DevcontainerAPIOptions = append(o.DevcontainerAPIOptions,
 				agentcontainers.WithContainerCLI(mLister),
+				agentcontainers.WithProjectDiscovery(false),
 				agentcontainers.WithContainerLabelIncludeFilter("this.label.does.not.exist.ignore.devcontainers", "true"),
 			)
 		})

cli/testdata/coder_agent_--help.golden

@@ -36,6 +36,9 @@ OPTIONS:
       --devcontainers-enable bool, $CODER_AGENT_DEVCONTAINERS_ENABLE (default: true)
           Allow the agent to automatically detect running devcontainers.
 
+      --devcontainers-project-discovery-enable bool, $CODER_AGENT_DEVCONTAINERS_PROJECT_DISCOVERY_ENABLE (default: true)
+          Allow the agent to search the filesystem for devcontainer projects.
+
       --log-dir string, $CODER_AGENT_LOG_DIR (default: /tmp)
           Specify the location for the agent log files.