Add a package listing API to cipd.

go/src/infra/tools/cipd/client.go

Index: go/src/infra/tools/cipd/client.go
diff --git a/go/src/infra/tools/cipd/client.go b/go/src/infra/tools/cipd/client.go
index e6e0c8906082fe1047ef43e2245f4b5598e4e87d..cf3015ea05ad1bbcaeddf148c35999b4f0915a91 100644
--- a/go/src/infra/tools/cipd/client.go
+++ b/go/src/infra/tools/cipd/client.go
@@ -41,6 +41,7 @@ import (
 	"io"
 	"net/http"
 	"os"
+	"sort"
 	"strings"
 	"time"
 
@@ -167,6 +168,9 @@ type Client interface {
 	// the site root. It doesn't check whether the instance is already deployed.
 	FetchAndDeployInstance(pin common.Pin) error
 
+	// ListPackages returns a list of strings of package names.
+	ListPackages(path string, recursive bool) ([]string, error)
+
 	// ProcessEnsureFile parses text file that describes what should be installed
 	// by EnsurePackages function. It is a text file where each line has a form:
 	// <package name> <desired version>. Whitespaces are ignored. Lines that start
@@ -278,6 +282,22 @@ func (client *clientImpl) ModifyACL(packagePath string, changes []PackageACLChan
 	return client.remote.modifyACL(packagePath, changes)
 }
 
+func (client *clientImpl) ListPackages(path string, recursive bool) ([]string, error) {
+	pkgs, dirs, err := client.remote.listPackages(path, recursive)
+	if err != nil {
+		return nil, err
+	}
+
+	// Add trailing slash to directories.
+	for k, d := range dirs {

[Vadim Sh., 2015/06/23 00:08:35]

IIUC, that's the only place where dir vs pkg matter now?

How about embracing "dir can be a package" situation and just display it in UI
somehow. Show both dir (with "/") and package without ("/"). (I think it happens
now).

I know at least one example of filesystem-like datamodel where directories are
no special from leaf nodes: zookeeper. So it's not unheard of. 

My concern is that trying to keep directories as a special kind of entities can
lead to more complications than gains.

[estaab, 2015/06/23 02:26:13]

Sounds fine, we show both now.

+		dirs[k] = d + "/"
+	}
+	// Merge and sort packages and directories.
+	allPkgs := append(pkgs, dirs...)
+	sort.Sort(sort.StringSlice(allPkgs))

[Vadim Sh., 2015/06/23 00:08:35]

sort.Strings(allPkgs)

[estaab, 2015/06/23 02:26:14]

Done.

+	return allPkgs, nil
+}
+
 func (client *clientImpl) UploadToCAS(sha1 string, data io.ReadSeeker, session *UploadSession) error {
 	// Open new upload session if an existing is not provided.
 	var err error
@@ -596,6 +616,8 @@ type remote interface {
 
 	attachTags(pin common.Pin, tags []string) error
 	fetchInstance(pin common.Pin) (*fetchInstanceResponse, error)
+
+	listPackages(path string, recursive bool) ([]string, []string, error)
 }
 
 type storage interface {