diff --git a/backend/_example/memory_store/go.mod b/backend/_example/memory_store/go.mod
index 1dc418ad..40910062 100644
--- a/backend/_example/memory_store/go.mod
+++ b/backend/_example/memory_store/go.mod
@@ -5,7 +5,6 @@ go 1.14
 require (
 	github.com/go-pkgz/jrpc v0.1.0
 	github.com/go-pkgz/lgr v0.7.0
-	github.com/jessevdk/go-flags v0.0.0-20180331124232-1c38ed7ad0cc
 	github.com/pkg/errors v0.9.1
 	github.com/rs/xid v1.2.1
 	github.com/stretchr/testify v1.5.1
diff --git a/backend/_example/memory_store/go.sum b/backend/_example/memory_store/go.sum
index cd7998e2..617ccdf2 100644
--- a/backend/_example/memory_store/go.sum
+++ b/backend/_example/memory_store/go.sum
@@ -157,6 +157,8 @@ github.com/tidwall/match v1.0.1/go.mod h1:LujAq0jyVjBy028G1WhWfIzbpQfMO8bBZ6Tyb0
 github.com/tidwall/pretty v1.0.0/go.mod h1:XNkn88O1ChpSDQmQeStsy+sBenx6DDtFZJxhVysOjyk=
 github.com/tidwall/rtree v0.0.0-20180113144539-6cd427091e0e/go.mod h1:/h+UnNGt0IhNNJLkGikcdcJqm66zGD/uJGMRxK/9+Ao=
 github.com/tidwall/tinyqueue v0.0.0-20180302190814-1e39f5511563/go.mod h1:mLqSmt7Dv/CNneF2wfcChfN1rvapyQr01LGKnKex0DQ=
+github.com/umputun/go-flags v0.0.0-20180331124232-1c38ed7ad0cc/go.mod h1:nvqHT2I0/X1L/Y0MrjF9GSLb6JCOnJwGfaDjgzSfAvs=
+github.com/umputun/go-flags v1.5.1/go.mod h1:nTbvsO/hKqe7Utri/NoyN18GR3+EWf+9RrmsdwdhrEc=
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
 github.com/valyala/fasthttp v1.0.0/go.mod h1:4vX61m6KN+xDduDNwXrhIAVZaZaZiQ1luJk8LWSxF3s=
 github.com/valyala/tcplisten v0.0.0-20161114210144-ceec8f93295a/go.mod h1:v3UYOV9WzVtRmSR+PDvWpU/qWl4Wa5LApYYX4ZtKbio=
diff --git a/backend/_example/memory_store/main.go b/backend/_example/memory_store/main.go
index b7751c91..67def3e0 100644
--- a/backend/_example/memory_store/main.go
+++ b/backend/_example/memory_store/main.go
@@ -12,7 +12,7 @@ import (
 
 	"github.com/go-pkgz/jrpc"
 	log "github.com/go-pkgz/lgr"
-	"github.com/jessevdk/go-flags"
+	"github.com/umputun/go-flags"
 
 	"github.com/umputun/remark/memory_store/accessor"
 	"github.com/umputun/remark/memory_store/server"
diff --git a/backend/app/cmd/avatar_test.go b/backend/app/cmd/avatar_test.go
index e31a53b8..43b3b476 100644
--- a/backend/app/cmd/avatar_test.go
+++ b/backend/app/cmd/avatar_test.go
@@ -6,9 +6,9 @@ import (
 	"testing"
 
 	"github.com/go-pkgz/auth/avatar"
-	flags "github.com/jessevdk/go-flags"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"github.com/umputun/go-flags"
 )
 
 func TestAvatar_Execute(t *testing.T) {
diff --git a/backend/app/cmd/backup_test.go b/backend/app/cmd/backup_test.go
index 60a8bf7e..babe7438 100644
--- a/backend/app/cmd/backup_test.go
+++ b/backend/app/cmd/backup_test.go
@@ -8,7 +8,8 @@ import (
 	"os"
 	"testing"
 
-	flags "github.com/jessevdk/go-flags"
+	"github.com/umputun/go-flags"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
diff --git a/backend/app/cmd/cleanup_test.go b/backend/app/cmd/cleanup_test.go
index 02ef3b70..829cef78 100644
--- a/backend/app/cmd/cleanup_test.go
+++ b/backend/app/cmd/cleanup_test.go
@@ -10,9 +10,9 @@ import (
 	"time"
 
 	"github.com/go-chi/chi"
-	flags "github.com/jessevdk/go-flags"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"github.com/umputun/go-flags"
 
 	"github.com/umputun/remark/backend/app/store"
 )
diff --git a/backend/app/cmd/import_test.go b/backend/app/cmd/import_test.go
index 94080520..127491a2 100644
--- a/backend/app/cmd/import_test.go
+++ b/backend/app/cmd/import_test.go
@@ -9,7 +9,8 @@ import (
 	"time"
 
 	log "github.com/go-pkgz/lgr"
-	flags "github.com/jessevdk/go-flags"
+	"github.com/umputun/go-flags"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
diff --git a/backend/app/cmd/remap_test.go b/backend/app/cmd/remap_test.go
index d215ffb4..d2625218 100644
--- a/backend/app/cmd/remap_test.go
+++ b/backend/app/cmd/remap_test.go
@@ -6,7 +6,8 @@ import (
 	"net/http/httptest"
 	"testing"
 
-	"github.com/jessevdk/go-flags"
+	"github.com/umputun/go-flags"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
diff --git a/backend/app/cmd/restore_test.go b/backend/app/cmd/restore_test.go
index 4ff59129..c7abf7aa 100644
--- a/backend/app/cmd/restore_test.go
+++ b/backend/app/cmd/restore_test.go
@@ -7,7 +7,8 @@ import (
 	"net/http/httptest"
 	"testing"
 
-	flags "github.com/jessevdk/go-flags"
+	"github.com/umputun/go-flags"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
diff --git a/backend/app/cmd/server_test.go b/backend/app/cmd/server_test.go
index 52577722..64e8a0cd 100644
--- a/backend/app/cmd/server_test.go
+++ b/backend/app/cmd/server_test.go
@@ -17,7 +17,7 @@ import (
 
 	"github.com/dgrijalva/jwt-go"
 	"github.com/go-pkgz/auth/token"
-	"github.com/jessevdk/go-flags"
+	"github.com/umputun/go-flags"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
diff --git a/backend/app/main.go b/backend/app/main.go
index 4fd6b51a..9ca2331a 100644
--- a/backend/app/main.go
+++ b/backend/app/main.go
@@ -8,7 +8,7 @@ import (
 	"syscall"
 
 	log "github.com/go-pkgz/lgr"
-	"github.com/jessevdk/go-flags"
+	"github.com/umputun/go-flags"
 
 	"github.com/umputun/remark/backend/app/cmd"
 )
diff --git a/backend/go.mod b/backend/go.mod
index f32d4673..051b2a6e 100644
--- a/backend/go.mod
+++ b/backend/go.mod
@@ -22,7 +22,6 @@ require (
 	github.com/google/uuid v1.1.1
 	github.com/gorilla/feeds v1.1.1
 	github.com/hashicorp/go-multierror v1.1.0
-	github.com/jessevdk/go-flags v0.0.0-20180331124232-1c38ed7ad0cc
 	github.com/kyokomi/emoji v2.2.1+incompatible
 	github.com/microcosm-cc/bluemonday v1.0.2
 	github.com/patrickmn/go-cache v2.1.0+incompatible
@@ -31,6 +30,7 @@ require (
 	github.com/rs/xid v1.2.1
 	github.com/russross/blackfriday/v2 v2.0.1
 	github.com/stretchr/testify v1.5.1
+	github.com/umputun/go-flags v1.5.1
 	go.etcd.io/bbolt v1.3.4
 	golang.org/x/crypto v0.0.0-20200406173513-056763e48d71
 	golang.org/x/image v0.0.0-20200119044424-58c23975cae1
diff --git a/backend/go.sum b/backend/go.sum
index a997a309..60f55299 100644
--- a/backend/go.sum
+++ b/backend/go.sum
@@ -130,10 +130,6 @@ github.com/hpcloud/tail v1.0.0 h1:nfCOvKYfkgYP8hkirhJocXT2+zOD8yUNjXaWfTlyFKI=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/imkira/go-interpol v1.1.0 h1:KIiKr0VSG2CUW1hl1jpiyuzuJeKUUpC8iM1AIE7N1Vk=
 github.com/imkira/go-interpol v1.1.0/go.mod h1:z0h2/2T3XF8kyEPpRgJ3kmNv+C43p+I/CoI+jC3w2iA=
-github.com/jessevdk/go-flags v0.0.0-20180331124232-1c38ed7ad0cc h1:0L2sGkaj6MWuV1BfXsrLJ/+XA8RzKKVsYlLVXNkK1Lw=
-github.com/jessevdk/go-flags v0.0.0-20180331124232-1c38ed7ad0cc/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
-github.com/jessevdk/go-flags v1.4.0 h1:4IU2WS7AumrZ/40jfhf4QVDMsQwqA7VEHozFRrGARJA=
-github.com/jessevdk/go-flags v1.4.0/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
 github.com/jstemmer/go-junit-report v0.0.0-20190106144839-af01ea7f8024/go.mod h1:6v2b51hI/fHJwM22ozAgKL4VKDeJcHhJFhtBdhmNjmU=
 github.com/jtolds/gls v4.2.1+incompatible h1:fSuqC+Gmlu6l/ZYAoZzx2pyucC8Xza35fpRVWLVmUEE=
 github.com/jtolds/gls v4.2.1+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
@@ -214,6 +210,8 @@ github.com/tidwall/rtree v0.0.0-20180113144539-6cd427091e0e h1:+NL1GDIUOKxVfbp2K
 github.com/tidwall/rtree v0.0.0-20180113144539-6cd427091e0e/go.mod h1:/h+UnNGt0IhNNJLkGikcdcJqm66zGD/uJGMRxK/9+Ao=
 github.com/tidwall/tinyqueue v0.0.0-20180302190814-1e39f5511563 h1:Otn9S136ELckZ3KKDyCkxapfufrqDqwmGjcHfAyXRrE=
 github.com/tidwall/tinyqueue v0.0.0-20180302190814-1e39f5511563/go.mod h1:mLqSmt7Dv/CNneF2wfcChfN1rvapyQr01LGKnKex0DQ=
+github.com/umputun/go-flags v1.5.1 h1:vRauoXV3Ultt1HrxivSxowbintgZLJE+EcBy5ta3/mY=
+github.com/umputun/go-flags v1.5.1/go.mod h1:nTbvsO/hKqe7Utri/NoyN18GR3+EWf+9RrmsdwdhrEc=
 github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
 github.com/valyala/fasthttp v1.0.0 h1:BwIoZQbBsTo3v2F5lz5Oy3TlTq4wLKTLV260EVTEWco=
diff --git a/backend/vendor/github.com/jessevdk/go-flags/.travis.yml b/backend/vendor/github.com/umputun/go-flags/.travis.yml
similarity index 94%
rename from backend/vendor/github.com/jessevdk/go-flags/.travis.yml
rename to backend/vendor/github.com/umputun/go-flags/.travis.yml
index 0f0728d2..06dbe728 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/.travis.yml
+++ b/backend/vendor/github.com/umputun/go-flags/.travis.yml
@@ -6,8 +6,6 @@ os:
 
 go:
   - 1.x
-  - 1.7.x
-  - 1.8.x
   - 1.9.x
   - 1.10.x
 
@@ -17,7 +15,7 @@ install:
   - go build -v ./...
 
   # linting
-  - go get github.com/golang/lint/golint
+  - go get -v golang.org/x/lint/golint
 
   # code coverage
   - go get golang.org/x/tools/cmd/cover
diff --git a/backend/vendor/github.com/jessevdk/go-flags/LICENSE b/backend/vendor/github.com/umputun/go-flags/LICENSE
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/LICENSE
rename to backend/vendor/github.com/umputun/go-flags/LICENSE
diff --git a/backend/vendor/github.com/jessevdk/go-flags/README.md b/backend/vendor/github.com/umputun/go-flags/README.md
similarity index 95%
rename from backend/vendor/github.com/jessevdk/go-flags/README.md
rename to backend/vendor/github.com/umputun/go-flags/README.md
index 3b02394e..f22650b2 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/README.md
+++ b/backend/vendor/github.com/umputun/go-flags/README.md
@@ -61,6 +61,9 @@ var opts struct {
 	// Example of a required flag
 	Name string `short:"n" long:"name" description:"A name" required:"true"`
 
+	// Example of a flag restricted to a pre-defined set of strings
+	Animal string `long:"animal" choice:"cat" choice:"dog"`
+
 	// Example of a value name
 	File string `short:"f" long:"file" description:"A file" value-name:"FILE"`
 
@@ -91,6 +94,7 @@ args := []string{
 	"-vv",
 	"--offset=5",
 	"-n", "Me",
+	"--animal", "dog", // anything other than "cat" or "dog" will raise an error
 	"-p", "3",
 	"-s", "hello",
 	"-s", "world",
@@ -115,6 +119,7 @@ if err != nil {
 fmt.Printf("Verbosity: %v\n", opts.Verbose)
 fmt.Printf("Offset: %d\n", opts.Offset)
 fmt.Printf("Name: %s\n", opts.Name)
+fmt.Printf("Animal: %s\n", opts.Animal)
 fmt.Printf("Ptr: %d\n", *opts.Ptr)
 fmt.Printf("StringSlice: %v\n", opts.StringSlice)
 fmt.Printf("PtrSlice: [%v %v]\n", *opts.PtrSlice[0], *opts.PtrSlice[1])
diff --git a/backend/vendor/github.com/jessevdk/go-flags/arg.go b/backend/vendor/github.com/umputun/go-flags/arg.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/arg.go
rename to backend/vendor/github.com/umputun/go-flags/arg.go
diff --git a/backend/vendor/github.com/jessevdk/go-flags/check_crosscompile.sh b/backend/vendor/github.com/umputun/go-flags/check_crosscompile.sh
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/check_crosscompile.sh
rename to backend/vendor/github.com/umputun/go-flags/check_crosscompile.sh
diff --git a/backend/vendor/github.com/jessevdk/go-flags/closest.go b/backend/vendor/github.com/umputun/go-flags/closest.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/closest.go
rename to backend/vendor/github.com/umputun/go-flags/closest.go
diff --git a/backend/vendor/github.com/jessevdk/go-flags/command.go b/backend/vendor/github.com/umputun/go-flags/command.go
similarity index 99%
rename from backend/vendor/github.com/jessevdk/go-flags/command.go
rename to backend/vendor/github.com/umputun/go-flags/command.go
index 486bacba..879465d7 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/command.go
+++ b/backend/vendor/github.com/umputun/go-flags/command.go
@@ -438,7 +438,7 @@ func (c *Command) match(name string) bool {
 	return false
 }
 
-func (c *Command) hasCliOptions() bool {
+func (c *Command) hasHelpOptions() bool {
 	ret := false
 
 	c.eachGroup(func(g *Group) {
@@ -447,7 +447,7 @@ func (c *Command) hasCliOptions() bool {
 		}
 
 		for _, opt := range g.options {
-			if opt.canCli() {
+			if opt.showInHelp() {
 				ret = true
 			}
 		}
diff --git a/backend/vendor/github.com/jessevdk/go-flags/completion.go b/backend/vendor/github.com/umputun/go-flags/completion.go
similarity index 98%
rename from backend/vendor/github.com/jessevdk/go-flags/completion.go
rename to backend/vendor/github.com/umputun/go-flags/completion.go
index 7a7a08b9..813a672c 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/completion.go
+++ b/backend/vendor/github.com/umputun/go-flags/completion.go
@@ -2,6 +2,7 @@ package flags
 
 import (
 	"fmt"
+	"os"
 	"path/filepath"
 	"reflect"
 	"sort"
@@ -62,6 +63,11 @@ func completionsWithoutDescriptions(items []string) []Completion {
 // prefix.
 func (f *Filename) Complete(match string) []Completion {
 	ret, _ := filepath.Glob(match + "*")
+	if len(ret) == 1 {
+		if info, err := os.Stat(ret[0]); err == nil && info.IsDir() {
+			ret[0] = ret[0] + "/"
+		}
+	}
 	return completionsWithoutDescriptions(ret)
 }
 
diff --git a/backend/vendor/github.com/jessevdk/go-flags/convert.go b/backend/vendor/github.com/umputun/go-flags/convert.go
similarity index 95%
rename from backend/vendor/github.com/jessevdk/go-flags/convert.go
rename to backend/vendor/github.com/umputun/go-flags/convert.go
index 984aac89..cda29b2f 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/convert.go
+++ b/backend/vendor/github.com/umputun/go-flags/convert.go
@@ -28,6 +28,15 @@ type Unmarshaler interface {
 	UnmarshalFlag(value string) error
 }
 
+// ValueValidator is the interface implemented by types that can validate a
+// flag argument themselves. The provided value is directly passed from the
+// command line.
+type ValueValidator interface {
+	// IsValidValue returns an error if the provided string value is valid for
+	// the flag.
+	IsValidValue(value string) error
+}
+
 func getBase(options multiTag, base int) (int, error) {
 	sbase := options.Get("base")
 
diff --git a/backend/vendor/github.com/jessevdk/go-flags/error.go b/backend/vendor/github.com/umputun/go-flags/error.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/error.go
rename to backend/vendor/github.com/umputun/go-flags/error.go
diff --git a/backend/vendor/github.com/jessevdk/go-flags/flags.go b/backend/vendor/github.com/umputun/go-flags/flags.go
similarity index 98%
rename from backend/vendor/github.com/jessevdk/go-flags/flags.go
rename to backend/vendor/github.com/umputun/go-flags/flags.go
index e627c99f..ac2157dd 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/flags.go
+++ b/backend/vendor/github.com/umputun/go-flags/flags.go
@@ -109,7 +109,8 @@ The following is a list of tags for struct fields supported by go-flags:
     value-name:     the name of the argument value (to be shown in the help)
                     (optional)
     choice:         limits the values for an option to a set of values.
-                    This tag can be specified multiple times (optional)
+                    Repeat this tag once for each allowable value.
+                    e.g. `long:"animal" choice:"cat" choice:"dog"`
     hidden:         if non-empty, the option is not visible in the help or man page.
 
     base: a base (radix) used to convert strings to integer values, the
diff --git a/backend/vendor/github.com/umputun/go-flags/go.mod b/backend/vendor/github.com/umputun/go-flags/go.mod
new file mode 100644
index 00000000..31425fa0
--- /dev/null
+++ b/backend/vendor/github.com/umputun/go-flags/go.mod
@@ -0,0 +1,3 @@
+module github.com/umputun/go-flags
+
+go 1.12
diff --git a/backend/vendor/github.com/jessevdk/go-flags/group.go b/backend/vendor/github.com/umputun/go-flags/group.go
similarity index 98%
rename from backend/vendor/github.com/jessevdk/go-flags/group.go
rename to backend/vendor/github.com/umputun/go-flags/group.go
index 9341d23f..ec909e51 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/group.go
+++ b/backend/vendor/github.com/umputun/go-flags/group.go
@@ -168,6 +168,18 @@ func (g *Group) optionByName(name string, namematch func(*Option, string) bool)
 	return retopt
 }
 
+func (g *Group) showInHelp() bool {
+	if g.Hidden {
+		return false
+	}
+	for _, opt := range g.options {
+		if opt.showInHelp() {
+			return true
+		}
+	}
+	return false
+}
+
 func (g *Group) eachGroup(f func(*Group)) {
 	f(g)
 
diff --git a/backend/vendor/github.com/jessevdk/go-flags/help.go b/backend/vendor/github.com/umputun/go-flags/help.go
similarity index 94%
rename from backend/vendor/github.com/jessevdk/go-flags/help.go
rename to backend/vendor/github.com/umputun/go-flags/help.go
index 8e3eba98..068fce15 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/help.go
+++ b/backend/vendor/github.com/umputun/go-flags/help.go
@@ -72,6 +72,9 @@ func (p *Parser) getAlignmentInfo() alignmentInfo {
 	var prevcmd *Command
 
 	p.eachActiveGroup(func(c *Command, grp *Group) {
+		if !grp.showInHelp() {
+			return
+		}
 		if c != prevcmd {
 			for _, arg := range c.args {
 				ret.updateLen(arg.Name, c != p.Command)
@@ -79,7 +82,7 @@ func (p *Parser) getAlignmentInfo() alignmentInfo {
 		}
 
 		for _, info := range grp.options {
-			if !info.canCli() {
+			if !info.showInHelp() {
 				continue
 			}
 
@@ -305,7 +308,7 @@ func (p *Parser) WriteHelp(writer io.Writer) {
 				}
 			} else if us, ok := allcmd.data.(Usage); ok {
 				usage = us.Usage()
-			} else if allcmd.hasCliOptions() {
+			} else if allcmd.hasHelpOptions() {
 				usage = fmt.Sprintf("[%s-OPTIONS]", allcmd.Name)
 			}
 
@@ -393,7 +396,7 @@ func (p *Parser) WriteHelp(writer io.Writer) {
 			}
 
 			for _, info := range grp.options {
-				if !info.canCli() || info.Hidden {
+				if !info.showInHelp() {
 					continue
 				}
 
@@ -489,3 +492,23 @@ func (p *Parser) WriteHelp(writer io.Writer) {
 
 	wr.Flush()
 }
+
+// WroteHelp is a helper to test the error from ParseArgs() to
+// determine if the help message was written. It is safe to
+// call without first checking that error is nil.
+func WroteHelp(err error) bool {
+	if err == nil { // No error
+		return false
+	}
+
+	flagError, ok := err.(*Error)
+	if !ok { // Not a go-flag error
+		return false
+	}
+
+	if flagError.Type != ErrHelp { // Did not print the help message
+		return false
+	}
+
+	return true
+}
diff --git a/backend/vendor/github.com/jessevdk/go-flags/ini.go b/backend/vendor/github.com/umputun/go-flags/ini.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/ini.go
rename to backend/vendor/github.com/umputun/go-flags/ini.go
diff --git a/backend/vendor/github.com/jessevdk/go-flags/man.go b/backend/vendor/github.com/umputun/go-flags/man.go
similarity index 92%
rename from backend/vendor/github.com/jessevdk/go-flags/man.go
rename to backend/vendor/github.com/umputun/go-flags/man.go
index c2cebae6..97372b76 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/man.go
+++ b/backend/vendor/github.com/umputun/go-flags/man.go
@@ -3,7 +3,9 @@ package flags
 import (
 	"fmt"
 	"io"
+	"os"
 	"runtime"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -38,7 +40,7 @@ func formatForMan(wr io.Writer, s string) {
 
 func writeManPageOptions(wr io.Writer, grp *Group) {
 	grp.eachGroup(func(group *Group) {
-		if group.Hidden || len(group.options) == 0 {
+		if !group.showInHelp() {
 			return
 		}
 
@@ -54,7 +56,7 @@ func writeManPageOptions(wr io.Writer, grp *Group) {
 		}
 
 		for _, opt := range group.options {
-			if !opt.canCli() || opt.Hidden {
+			if !opt.showInHelp() {
 				continue
 			}
 
@@ -148,12 +150,12 @@ func writeManPageCommand(wr io.Writer, name string, root *Command, command *Comm
 	var usage string
 	if us, ok := command.data.(Usage); ok {
 		usage = us.Usage()
-	} else if command.hasCliOptions() {
+	} else if command.hasHelpOptions() {
 		usage = fmt.Sprintf("[%s-OPTIONS]", command.Name)
 	}
 
 	var pre string
-	if root.hasCliOptions() {
+	if root.hasHelpOptions() {
 		pre = fmt.Sprintf("%s [OPTIONS] %s", root.Name, command.Name)
 	} else {
 		pre = fmt.Sprintf("%s %s", root.Name, command.Name)
@@ -175,6 +177,14 @@ func writeManPageCommand(wr io.Writer, name string, root *Command, command *Comm
 // writer.
 func (p *Parser) WriteManPage(wr io.Writer) {
 	t := time.Now()
+	source_date_epoch := os.Getenv("SOURCE_DATE_EPOCH")
+	if source_date_epoch != "" {
+		sde, err := strconv.ParseInt(source_date_epoch, 10, 64)
+		if err != nil {
+			panic(fmt.Sprintf("Invalid SOURCE_DATE_EPOCH: %s", err))
+		}
+		t = time.Unix(sde, 0)
+	}
 
 	fmt.Fprintf(wr, ".TH %s 1 \"%s\"\n", manQuote(p.Name), t.Format("2 January 2006"))
 	fmt.Fprintln(wr, ".SH NAME")
diff --git a/backend/vendor/github.com/jessevdk/go-flags/multitag.go b/backend/vendor/github.com/umputun/go-flags/multitag.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/multitag.go
rename to backend/vendor/github.com/umputun/go-flags/multitag.go
diff --git a/backend/vendor/github.com/jessevdk/go-flags/option.go b/backend/vendor/github.com/umputun/go-flags/option.go
similarity index 93%
rename from backend/vendor/github.com/jessevdk/go-flags/option.go
rename to backend/vendor/github.com/umputun/go-flags/option.go
index c681c39d..5cebb54c 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/option.go
+++ b/backend/vendor/github.com/umputun/go-flags/option.go
@@ -280,8 +280,8 @@ func (option *Option) set(value *string) error {
 	return convert("", option.value, option.tag)
 }
 
-func (option *Option) canCli() bool {
-	return option.ShortName != 0 || len(option.LongName) != 0
+func (option *Option) showInHelp() bool {
+	return !option.Hidden && (option.ShortName != 0 || len(option.LongName) != 0)
 }
 
 func (option *Option) canArgument() bool {
@@ -389,6 +389,30 @@ func (option *Option) isUnmarshaler() Unmarshaler {
 	return nil
 }
 
+func (option *Option) isValueValidator() ValueValidator {
+	v := option.value
+
+	for {
+		if !v.CanInterface() {
+			break
+		}
+
+		i := v.Interface()
+
+		if u, ok := i.(ValueValidator); ok {
+			return u
+		}
+
+		if !v.CanAddr() {
+			break
+		}
+
+		v = v.Addr()
+	}
+
+	return nil
+}
+
 func (option *Option) isBool() bool {
 	tp := option.value.Type()
 
@@ -507,3 +531,13 @@ func (option *Option) shortAndLongName() string {
 
 	return ret.String()
 }
+
+func (option *Option) isValidValue(arg string) error {
+	if validator := option.isValueValidator(); validator != nil {
+		return validator.IsValidValue(arg)
+	}
+	if argumentIsOption(arg) && !(option.isSignedNumber() && len(arg) > 1 && arg[0] == '-' && arg[1] >= '0' && arg[1] <= '9') {
+		return fmt.Errorf("expected argument for flag `%s', but got option `%s'", option, arg)
+	}
+	return nil
+}
diff --git a/backend/vendor/github.com/jessevdk/go-flags/optstyle_other.go b/backend/vendor/github.com/umputun/go-flags/optstyle_other.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/optstyle_other.go
rename to backend/vendor/github.com/umputun/go-flags/optstyle_other.go
diff --git a/backend/vendor/github.com/jessevdk/go-flags/optstyle_windows.go b/backend/vendor/github.com/umputun/go-flags/optstyle_windows.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/optstyle_windows.go
rename to backend/vendor/github.com/umputun/go-flags/optstyle_windows.go
diff --git a/backend/vendor/github.com/jessevdk/go-flags/parser.go b/backend/vendor/github.com/umputun/go-flags/parser.go
similarity index 96%
rename from backend/vendor/github.com/jessevdk/go-flags/parser.go
rename to backend/vendor/github.com/umputun/go-flags/parser.go
index 042930c4..a5347b0a 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/parser.go
+++ b/backend/vendor/github.com/umputun/go-flags/parser.go
@@ -241,6 +241,7 @@ func (p *Parser) ParseArgs(args []string) ([]string, error) {
 	p.fillParseState(s)
 
 	for !s.eof() {
+		var err error
 		arg := s.pop()
 
 		// When PassDoubleDash is set and we encounter a --, then
@@ -251,6 +252,20 @@ func (p *Parser) ParseArgs(args []string) ([]string, error) {
 		}
 
 		if !argumentIsOption(arg) {
+			if (p.Options&PassAfterNonOption) != None && s.lookup.commands[arg] == nil {
+				// If PassAfterNonOption is set then all remaining arguments
+				// are considered positional
+				if err = s.addArgs(s.arg); err != nil {
+					break
+				}
+
+				if err = s.addArgs(s.args...); err != nil {
+					break
+				}
+
+				break
+			}
+
 			// Note: this also sets s.err, so we can just check for
 			// nil here and use s.err later
 			if p.parseNonOption(s) != nil {
@@ -260,8 +275,6 @@ func (p *Parser) ParseArgs(args []string) ([]string, error) {
 			continue
 		}
 
-		var err error
-
 		prefix, optname, islong := stripOptionPrefix(arg)
 		optname, _, argument := splitOption(prefix, optname, islong)
 
@@ -519,8 +532,8 @@ func (p *Parser) parseOption(s *parseState, name string, option *Option, canarg
 		} else {
 			arg = s.pop()
 
-			if argumentIsOption(arg) && !(option.isSignedNumber() && len(arg) > 1 && arg[0] == '-' && arg[1] >= '0' && arg[1] <= '9') {
-				return newErrorf(ErrExpectedArgument, "expected argument for flag `%s', but got option `%s'", option, arg)
+			if validationErr := option.isValidValue(arg); validationErr != nil {
+				return newErrorf(ErrExpectedArgument, validationErr.Error())
 			} else if p.Options&PassDoubleDash != 0 && arg == "--" {
 				return newErrorf(ErrExpectedArgument, "expected argument for flag `%s', but got double dash `--'", option)
 			}
@@ -653,23 +666,7 @@ func (p *Parser) parseNonOption(s *parseState) error {
 		}
 	}
 
-	if (p.Options & PassAfterNonOption) != None {
-		// If PassAfterNonOption is set then all remaining arguments
-		// are considered positional
-		if err := s.addArgs(s.arg); err != nil {
-			return err
-		}
-
-		if err := s.addArgs(s.args...); err != nil {
-			return err
-		}
-
-		s.args = []string{}
-	} else {
-		return s.addArgs(s.arg)
-	}
-
-	return nil
+	return s.addArgs(s.arg)
 }
 
 func (p *Parser) showBuiltinHelp() error {
diff --git a/backend/vendor/github.com/jessevdk/go-flags/termsize.go b/backend/vendor/github.com/umputun/go-flags/termsize.go
similarity index 86%
rename from backend/vendor/github.com/jessevdk/go-flags/termsize.go
rename to backend/vendor/github.com/umputun/go-flags/termsize.go
index 1ca6a850..29b1110b 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/termsize.go
+++ b/backend/vendor/github.com/umputun/go-flags/termsize.go
@@ -1,4 +1,4 @@
-// +build !windows,!plan9,!solaris,!appengine
+// +build !windows,!plan9,!solaris,!appengine,!wasm
 
 package flags
 
diff --git a/backend/vendor/github.com/jessevdk/go-flags/termsize_nosysioctl.go b/backend/vendor/github.com/umputun/go-flags/termsize_nosysioctl.go
similarity index 59%
rename from backend/vendor/github.com/jessevdk/go-flags/termsize_nosysioctl.go
rename to backend/vendor/github.com/umputun/go-flags/termsize_nosysioctl.go
index 3d5385b0..12a54580 100644
--- a/backend/vendor/github.com/jessevdk/go-flags/termsize_nosysioctl.go
+++ b/backend/vendor/github.com/umputun/go-flags/termsize_nosysioctl.go
@@ -1,4 +1,4 @@
-// +build windows plan9 solaris appengine
+// +build plan9 solaris appengine wasm
 
 package flags
 
diff --git a/backend/vendor/github.com/umputun/go-flags/termsize_windows.go b/backend/vendor/github.com/umputun/go-flags/termsize_windows.go
new file mode 100644
index 00000000..5c0fa6ba
--- /dev/null
+++ b/backend/vendor/github.com/umputun/go-flags/termsize_windows.go
@@ -0,0 +1,85 @@
+// +build windows
+
+package flags
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+type (
+	SHORT int16
+	WORD  uint16
+
+	SMALL_RECT struct {
+		Left   SHORT
+		Top    SHORT
+		Right  SHORT
+		Bottom SHORT
+	}
+
+	COORD struct {
+		X SHORT
+		Y SHORT
+	}
+
+	CONSOLE_SCREEN_BUFFER_INFO struct {
+		Size              COORD
+		CursorPosition    COORD
+		Attributes        WORD
+		Window            SMALL_RECT
+		MaximumWindowSize COORD
+	}
+)
+
+var kernel32DLL = syscall.NewLazyDLL("kernel32.dll")
+var getConsoleScreenBufferInfoProc = kernel32DLL.NewProc("GetConsoleScreenBufferInfo")
+
+func getError(r1, r2 uintptr, lastErr error) error {
+	// If the function fails, the return value is zero.
+	if r1 == 0 {
+		if lastErr != nil {
+			return lastErr
+		}
+		return syscall.EINVAL
+	}
+	return nil
+}
+
+func getStdHandle(stdhandle int) (uintptr, error) {
+	handle, err := syscall.GetStdHandle(stdhandle)
+	if err != nil {
+		return 0, err
+	}
+	return uintptr(handle), nil
+}
+
+// GetConsoleScreenBufferInfo retrieves information about the specified console screen buffer.
+// http://msdn.microsoft.com/en-us/library/windows/desktop/ms683171(v=vs.85).aspx
+func GetConsoleScreenBufferInfo(handle uintptr) (*CONSOLE_SCREEN_BUFFER_INFO, error) {
+	var info CONSOLE_SCREEN_BUFFER_INFO
+	if err := getError(getConsoleScreenBufferInfoProc.Call(handle, uintptr(unsafe.Pointer(&info)), 0)); err != nil {
+		return nil, err
+	}
+	return &info, nil
+}
+
+func getTerminalColumns() int {
+	defaultWidth := 80
+
+	stdoutHandle, err := getStdHandle(syscall.STD_OUTPUT_HANDLE)
+	if err != nil {
+		return defaultWidth
+	}
+
+	info, err := GetConsoleScreenBufferInfo(stdoutHandle)
+	if err != nil {
+		return defaultWidth
+	}
+
+	if info.MaximumWindowSize.X > 0 {
+		return int(info.MaximumWindowSize.X)
+	}
+
+	return defaultWidth
+}
diff --git a/backend/vendor/github.com/jessevdk/go-flags/tiocgwinsz_bsdish.go b/backend/vendor/github.com/umputun/go-flags/tiocgwinsz_bsdish.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/tiocgwinsz_bsdish.go
rename to backend/vendor/github.com/umputun/go-flags/tiocgwinsz_bsdish.go
diff --git a/backend/vendor/github.com/jessevdk/go-flags/tiocgwinsz_linux.go b/backend/vendor/github.com/umputun/go-flags/tiocgwinsz_linux.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/tiocgwinsz_linux.go
rename to backend/vendor/github.com/umputun/go-flags/tiocgwinsz_linux.go
diff --git a/backend/vendor/github.com/jessevdk/go-flags/tiocgwinsz_other.go b/backend/vendor/github.com/umputun/go-flags/tiocgwinsz_other.go
similarity index 100%
rename from backend/vendor/github.com/jessevdk/go-flags/tiocgwinsz_other.go
rename to backend/vendor/github.com/umputun/go-flags/tiocgwinsz_other.go
diff --git a/backend/vendor/modules.txt b/backend/vendor/modules.txt
index 58be952d..30cb119d 100644
--- a/backend/vendor/modules.txt
+++ b/backend/vendor/modules.txt
@@ -1,13 +1,10 @@
 # cloud.google.com/go v0.40.0
 cloud.google.com/go/compute/metadata
 # github.com/Depado/bfchroma v1.2.0
-## explicit
 github.com/Depado/bfchroma
 # github.com/PuerkitoBio/goquery v1.5.1
-## explicit
 github.com/PuerkitoBio/goquery
 # github.com/alecthomas/chroma v0.7.2
-## explicit
 github.com/alecthomas/chroma
 github.com/alecthomas/chroma/formatters/html
 github.com/alecthomas/chroma/lexers
@@ -48,32 +45,25 @@ github.com/davecgh/go-spew/spew
 github.com/dghubble/oauth1
 github.com/dghubble/oauth1/twitter
 # github.com/dgrijalva/jwt-go v3.2.0+incompatible
-## explicit
 github.com/dgrijalva/jwt-go
 # github.com/didip/tollbooth v4.0.2+incompatible
-## explicit
 github.com/didip/tollbooth
 github.com/didip/tollbooth/errors
 github.com/didip/tollbooth/libstring
 github.com/didip/tollbooth/limiter
 # github.com/didip/tollbooth_chi v0.0.0-20170928041846-6ab5f3083f3d
-## explicit
 github.com/didip/tollbooth_chi
 # github.com/dlclark/regexp2 v1.1.6
 github.com/dlclark/regexp2
 github.com/dlclark/regexp2/syntax
 # github.com/go-chi/chi v4.1.0+incompatible
-## explicit
 github.com/go-chi/chi
 github.com/go-chi/chi/middleware
 # github.com/go-chi/cors v1.1.1
-## explicit
 github.com/go-chi/cors
 # github.com/go-chi/render v1.0.1
-## explicit
 github.com/go-chi/render
 # github.com/go-pkgz/auth v0.10.1
-## explicit
 github.com/go-pkgz/auth
 github.com/go-pkgz/auth/avatar
 github.com/go-pkgz/auth/logger
@@ -82,24 +72,18 @@ github.com/go-pkgz/auth/provider
 github.com/go-pkgz/auth/provider/sender
 github.com/go-pkgz/auth/token
 # github.com/go-pkgz/jrpc v0.1.0
-## explicit
 github.com/go-pkgz/jrpc
 # github.com/go-pkgz/lcw v0.5.0
-## explicit
 github.com/go-pkgz/lcw
 # github.com/go-pkgz/lgr v0.7.0
-## explicit
 github.com/go-pkgz/lgr
 # github.com/go-pkgz/repeater v1.1.3
-## explicit
 github.com/go-pkgz/repeater
 github.com/go-pkgz/repeater/strategy
 # github.com/go-pkgz/rest v1.5.0
-## explicit
 github.com/go-pkgz/rest
 github.com/go-pkgz/rest/logger
 # github.com/go-pkgz/syncs v1.1.1
-## explicit
 github.com/go-pkgz/syncs
 # github.com/go-redis/redis/v7 v7.0.0-beta.4
 github.com/go-redis/redis/v7
@@ -116,62 +100,49 @@ github.com/golang/protobuf/proto
 # github.com/golang/snappy v0.0.1
 github.com/golang/snappy
 # github.com/google/uuid v1.1.1
-## explicit
 github.com/google/uuid
 # github.com/gorilla/feeds v1.1.1
-## explicit
 github.com/gorilla/feeds
 # github.com/hashicorp/errwrap v1.0.0
 github.com/hashicorp/errwrap
 # github.com/hashicorp/go-multierror v1.1.0
-## explicit
 github.com/hashicorp/go-multierror
 # github.com/hashicorp/golang-lru v0.5.3
 github.com/hashicorp/golang-lru
 github.com/hashicorp/golang-lru/simplelru
-# github.com/jessevdk/go-flags v0.0.0-20180331124232-1c38ed7ad0cc
-## explicit
-github.com/jessevdk/go-flags
 # github.com/kyokomi/emoji v2.2.1+incompatible
-## explicit
 github.com/kyokomi/emoji
 # github.com/microcosm-cc/bluemonday v1.0.2
-## explicit
 github.com/microcosm-cc/bluemonday
 # github.com/nullrocks/identicon v0.0.0-20180626043057-7875f45b0022
 github.com/nullrocks/identicon
 # github.com/patrickmn/go-cache v2.1.0+incompatible
-## explicit
 github.com/patrickmn/go-cache
 # github.com/pkg/errors v0.9.1
-## explicit
 github.com/pkg/errors
 # github.com/pmezard/go-difflib v1.0.0
 github.com/pmezard/go-difflib/difflib
 # github.com/rakyll/statik v0.1.7
-## explicit
 github.com/rakyll/statik/fs
 # github.com/rs/xid v1.2.1
-## explicit
 github.com/rs/xid
 # github.com/russross/blackfriday/v2 v2.0.1
-## explicit
 github.com/russross/blackfriday/v2
 # github.com/shurcooL/sanitized_anchor_name v1.0.0
 github.com/shurcooL/sanitized_anchor_name
 # github.com/stretchr/objx v0.1.0
 github.com/stretchr/objx
 # github.com/stretchr/testify v1.5.1
-## explicit
 github.com/stretchr/testify/assert
 github.com/stretchr/testify/mock
 github.com/stretchr/testify/require
+# github.com/umputun/go-flags v1.5.1
+github.com/umputun/go-flags
 # github.com/xdg/scram v0.0.0-20180814205039-7eeb5667e42c
 github.com/xdg/scram
 # github.com/xdg/stringprep v1.0.0
 github.com/xdg/stringprep
 # go.etcd.io/bbolt v1.3.4
-## explicit
 go.etcd.io/bbolt
 # go.mongodb.org/mongo-driver v1.1.1
 go.mongodb.org/mongo-driver/bson
@@ -204,16 +175,13 @@ go.mongodb.org/mongo-driver/x/mongo/driver/topology
 go.mongodb.org/mongo-driver/x/mongo/driver/uuid
 go.mongodb.org/mongo-driver/x/mongo/driver/wiremessage
 # golang.org/x/crypto v0.0.0-20200406173513-056763e48d71
-## explicit
 golang.org/x/crypto/acme
 golang.org/x/crypto/acme/autocert
 golang.org/x/crypto/pbkdf2
 # golang.org/x/image v0.0.0-20200119044424-58c23975cae1
-## explicit
 golang.org/x/image/draw
 golang.org/x/image/math/f64
 # golang.org/x/net v0.0.0-20200202094626-16171245cfb2
-## explicit
 golang.org/x/net/context
 golang.org/x/net/context/ctxhttp
 golang.org/x/net/html