Allow for user specific themes (#5668)

* add migration and basic UI for changing a user's theme

* update user themem

* use right text on button

* load theme based on users' selection

* load theme based on users' selection in pwa too

* update sample config

* delete older theme loading

* implement AfterLoad to set users' theme properly

* set up default theme when creating a user. This uses the installation wide theme

* use flash messages for error

* set default theme when creating a user from the cli

* fix @lunny review

3 files changed, 31 insertions, 4 deletions

diff --git a/modules/auth/user_form.go b/modules/auth/user_form.go
index c281672fe1..f59b795b4e 100644
--- a/modules/auth/user_form.go
+++ b/modules/auth/user_form.go
@@ -12,7 +12,7 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 
 	"github.com/go-macaron/binding"
-	"gopkg.in/macaron.v1"
+	macaron "gopkg.in/macaron.v1"
 )
 
 // InstallForm form for installation page
@@ -189,6 +189,30 @@ func (f *AddEmailForm) Validate(ctx *macaron.Context, errs binding.Errors) bindi
 	return validate(errs, ctx.Data, f, ctx.Locale)
 }
 
+// UpdateThemeForm form for updating a users' theme
+type UpdateThemeForm struct {
+	Theme string `binding:"Required;MaxSize(30)"`
+}
+
+// Validate validates the field
+func (f *UpdateThemeForm) Validate(ctx *macaron.Context, errs binding.Errors) binding.Errors {
+	return validate(errs, ctx.Data, f, ctx.Locale)
+}
+
+// IsThemeExists checks if the theme is a theme available in the config.
+func (f UpdateThemeForm) IsThemeExists() bool {
+	var exists bool
+
+	for _, v := range setting.UI.Themes {
+		if strings.ToLower(v) == strings.ToLower(f.Theme) {
+			exists = true
+			break
+		}
+	}
+
+	return exists
+}
+
 // ChangePasswordForm form for changing password
 type ChangePasswordForm struct {
 	OldPassword string `form:"old_password" binding:"MaxSize(255)"`
diff --git a/modules/setting/defaults.go b/modules/setting/defaults.go
index 7630d10090..48257284c7 100644
--- a/modules/setting/defaults.go
+++ b/modules/setting/defaults.go
@@ -8,4 +8,5 @@ var (
 	defaultLangs                             = strings.Split("en-US,zh-CN,zh-HK,zh-TW,de-DE,fr-FR,nl-NL,lv-LV,ru-RU,uk-UA,ja-JP,es-ES,pt-BR,pl-PL,bg-BG,it-IT,fi-FI,tr-TR,cs-CZ,sr-SP,sv-SE,ko-KR", ",")
 	defaultLangNames                         = strings.Split("English,简体中文,繁體中文（香港）,繁體中文（台灣）,Deutsch,français,Nederlands,latviešu,русский,Українська,日本語,español,português do Brasil,polski,български,italiano,suomi,Türkçe,čeština,српски,svenska,한국어", ",")
 	defaultPullRequestWorkInProgressPrefixes = strings.Split("WIP:,[WIP]", ",")
+	defaultThemes                            = strings.Split("gitea", "arc-green")
 )
diff --git a/modules/setting/setting.go b/modules/setting/setting.go
index 23304453d2..88101937e9 100644
--- a/modules/setting/setting.go
+++ b/modules/setting/setting.go
@@ -33,9 +33,9 @@ import (
 	"github.com/go-macaron/session"
 	_ "github.com/go-macaron/session/redis" // redis plugin for store session
 	"github.com/go-xorm/core"
-	"github.com/kballard/go-shellquote"
-	"github.com/mcuadros/go-version"
-	"gopkg.in/ini.v1"
+	shellquote "github.com/kballard/go-shellquote"
+	version "github.com/mcuadros/go-version"
+	ini "gopkg.in/ini.v1"
 	"strk.kbt.io/projects/go/libravatar"
 )
 
@@ -303,6 +303,7 @@ var (
 		MaxDisplayFileSize  int64
 		ShowUserEmail       bool
 		DefaultTheme        string
+		Themes              []string
 
 		Admin struct {
 			UserPagingNum   int
@@ -329,6 +330,7 @@ var (
 		ThemeColorMetaTag:   `#6cc644`,
 		MaxDisplayFileSize:  8388608,
 		DefaultTheme:        `gitea`,
+		Themes:              []string{`gitea`, `arc-green`},
 		Admin: struct {
 			UserPagingNum   int
 			RepoPagingNum   int