kbfsgit: support the lfs init command, and start in LFS mode

If the arguments to the `git-remote-keybase` process are something
like "lfs origin keybase://type/name/repo".

Issue: HOTPOT-1273

go/kbfs/kbfsgit/git-remote-keybase/main.go

@@ -124,15 +124,17 @@ func start() (startErr *libfs.Error) {
 
 	remote := flag.Arg(0)
 	var repo string
+	lfs := false
 	if len(flag.Args()) > 1 {
 		repo = flag.Arg(1)
 	} else {
 		// For LFS invocation, the arguments actually come together in
 		// a single quoted argument for some reason.
 		s := strings.Split(remote, " ")
-		if len(s) > 1 {
-			remote = s[0]
-			repo = s[1]
+		if len(s) > 2 {
+			lfs = s[0] == "lfs"
+			remote = s[1]
+			repo = s[2]
 		}
 	}
 
@@ -146,11 +148,13 @@ func start() (startErr *libfs.Error) {
 		Remote:     remote,
 		Repo:       repo,
 		GitDir:     getLocalGitDir(),
+		LFS:        lfs,
 	}
 
 	ctx := context.Background()
 	return kbfsgit.Start(
-		ctx, options, kbCtx, defaultLogPath, os.Stdin, os.Stdout, stderrFile)
+		ctx, options, kbCtx, defaultLogPath, os.Stdin, os.Stdout,
+		stderrFile)
 }
 
 func main() {

go/kbfs/kbfsgit/runner.go

@@ -55,6 +55,7 @@ const (
 	gitOptionPushcert  = "pushcert"
 	gitOptionIfAsked   = "if-asked"
 
+	gitLFSInitEvent      = "init"
 	gitLFSUploadEvent    = "upload"
 	gitLFSCompleteEvent  = "complete"
 	gitLFSTerminateEvent = "terminate"
@@ -2048,10 +2049,12 @@ type lfsError struct {
 }
 
 type lfsRequest struct {
-	Event string `json:"event"`
-	Oid   string `json:"oid"`
-	Size  int    `json:"size,omitempty"`
-	Path  string `json:"path,omitempty"`
+	Event     string `json:"event"`
+	Oid       string `json:"oid"`
+	Size      int    `json:"size,omitempty"`
+	Path      string `json:"path,omitempty"`
+	Operation string `json:"operation,omitempty"`
+	Remote    string `json:"remote,omitempty"`
 }
 
 type lfsResponse struct {
@@ -2062,6 +2065,7 @@ type lfsResponse struct {
 
 func (r *runner) processCommandLFS(
 	ctx context.Context, commandChan <-chan string) (err error) {
+lfsLoop:
 	for {
 		select {
 		case cmd := <-commandChan:
@@ -2079,6 +2083,15 @@ func (r *runner) processCommandLFS(
 				Oid:   req.Oid,
 			}
 			switch req.Event {
+			case gitLFSInitEvent:
+				r.log.CDebugf(
+					ctx, "Initialize message, operation=%s, remote=%s",
+					req.Operation, req.Remote)
+				_, err := r.output.Write([]byte("{}\n"))
+				if err != nil {
+					return err
+				}
+				continue lfsLoop
 			case gitLFSUploadEvent:
 				r.log.CDebugf(ctx, "Handling upload, oid=%s", req.Oid)
 				err := r.handleLFSUpload(ctx, req.Oid, req.Path)

go/kbfs/kbfsgit/start.go

@@ -25,6 +25,9 @@ type StartOptions struct {
 	// GitDir is the filepath leading to the .git directory of the
 	// caller's local on-disk repo.
 	GitDir string
+	// LFS indicates whether we should listen for LFS commands instead
+	// of normal git commands.
+	LFS bool
 }
 
 // Start starts the kbfsgit logic, and begins listening for git
@@ -61,9 +64,13 @@ func Start(ctx context.Context, options StartOptions,
 		return libfs.InitError(err.Error())
 	}
 
-	r, err := newRunner(
+	t := processGit
+	if options.LFS {
+		t = processLFS
+	}
+	r, err := newRunnerWithType(
 		ctx, config, options.Remote, options.Repo, options.GitDir,
-		input, output, errput)
+		input, output, errput, t)
 	if err != nil {
 		return libfs.InitError(err.Error())
 	}