Redirect on changed user and org name (#11649)

* Add redirect for user

* Add redirect for orgs

* Add user redirect test

* Appease linter

* Add comment to DeleteUserRedirect function

* Fix locale changes

* Fix GetUserByParams

* Fix orgAssignment

* Remove debug logging

* Add redirect prompt

* Dont Export DeleteUserRedirect & only use it within a session

* Unexport newUserRedirect

* cleanup

* Fix & Dedub API code

* Format Template

* Add Migration & rm dublicat

* Refactor: unexport newRepoRedirect() & rm dedub del exec

* if this fails we'll need to re-rename the user directory

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

25 files changed, 325 insertions, 64 deletions

diff --git a/models/error.go b/models/error.go
index 7f1eda1b14..fc161ed806 100644
--- a/models/error.go
+++ b/models/error.go
@@ -146,6 +146,21 @@ func (err ErrUserNotExist) Error() string {
 	return fmt.Sprintf("user does not exist [uid: %d, name: %s, keyid: %d]", err.UID, err.Name, err.KeyID)
 }
 
+// ErrUserRedirectNotExist represents a "UserRedirectNotExist" kind of error.
+type ErrUserRedirectNotExist struct {
+	Name string
+}
+
+// IsErrUserRedirectNotExist check if an error is an ErrUserRedirectNotExist.
+func IsErrUserRedirectNotExist(err error) bool {
+	_, ok := err.(ErrUserRedirectNotExist)
+	return ok
+}
+
+func (err ErrUserRedirectNotExist) Error() string {
+	return fmt.Sprintf("user redirect does not exist [name: %s]", err.Name)
+}
+
 // ErrUserProhibitLogin represents a "ErrUserProhibitLogin" kind of error.
 type ErrUserProhibitLogin struct {
 	UID  int64
diff --git a/models/fixtures/user_redirect.yml b/models/fixtures/user_redirect.yml
new file mode 100644
index 0000000000..8ff7993398
--- /dev/null
+++ b/models/fixtures/user_redirect.yml
@@ -0,0 +1,4 @@
+-
+  id: 1
+  lower_name: olduser1
+  redirect_user_id: 1
diff --git a/models/migrations/migrations.go b/models/migrations/migrations.go
index f62bba2a71..3227f6f754 100644
--- a/models/migrations/migrations.go
+++ b/models/migrations/migrations.go
@@ -279,6 +279,8 @@ var migrations = []Migration{
 	NewMigration("Convert hook task type from char(16) to varchar(16) and trim the column", convertHookTaskTypeToVarcharAndTrim),
 	// v166 -> v167
 	NewMigration("Where Password is Valid with Empty String delete it", recalculateUserEmptyPWD),
+	// v167 -> v168
+	NewMigration("Add user redirect", addUserRedirect),
 }
 
 // GetCurrentDBVersion returns the current db version
diff --git a/models/migrations/v167.go b/models/migrations/v167.go
new file mode 100644
index 0000000000..fd91f226ab
--- /dev/null
+++ b/models/migrations/v167.go
@@ -0,0 +1,24 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"fmt"
+
+	"xorm.io/xorm"
+)
+
+func addUserRedirect(x *xorm.Engine) (err error) {
+	type UserRedirect struct {
+		ID             int64  `xorm:"pk autoincr"`
+		LowerName      string `xorm:"UNIQUE(s) INDEX NOT NULL"`
+		RedirectUserID int64
+	}
+
+	if err := x.Sync2(new(UserRedirect)); err != nil {
+		return fmt.Errorf("Sync2: %v", err)
+	}
+	return nil
+}
diff --git a/models/models.go b/models/models.go
index 2ace1ea6dd..1bfe75b7fc 100644
--- a/models/models.go
+++ b/models/models.go
@@ -128,6 +128,7 @@ func init() {
 		new(Task),
 		new(LanguageStat),
 		new(EmailHash),
+		new(UserRedirect),
 		new(Project),
 		new(ProjectBoard),
 		new(ProjectIssue),
diff --git a/models/org.go b/models/org.go
index f45c9af7a7..ee867eec88 100644
--- a/models/org.go
+++ b/models/org.go
@@ -171,6 +171,10 @@ func CreateOrganization(org, owner *User) (err error) {
 		return err
 	}
 
+	if err = deleteUserRedirect(sess, org.Name); err != nil {
+		return err
+	}
+
 	if _, err = sess.Insert(org); err != nil {
 		return fmt.Errorf("insert organization: %v", err)
 	}
diff --git a/models/repo.go b/models/repo.go
index b11671e1fc..62d64fbee9 100644
--- a/models/repo.go
+++ b/models/repo.go
@@ -1312,8 +1312,8 @@ func TransferOwnership(doer *User, newOwnerName string, repo *Repository) error
 		return fmt.Errorf("delete repo redirect: %v", err)
 	}
 
-	if err := NewRepoRedirect(DBContext{sess}, oldOwner.ID, repo.ID, repo.Name, repo.Name); err != nil {
-		return fmt.Errorf("NewRepoRedirect: %v", err)
+	if err := newRepoRedirect(sess, oldOwner.ID, repo.ID, repo.Name, repo.Name); err != nil {
+		return fmt.Errorf("newRepoRedirect: %v", err)
 	}
 
 	return sess.Commit()
@@ -1361,12 +1361,7 @@ func ChangeRepositoryName(doer *User, repo *Repository, newRepoName string) (err
 		return fmt.Errorf("sess.Begin: %v", err)
 	}
 
-	// If there was previously a redirect at this location, remove it.
-	if err = deleteRepoRedirect(sess, repo.OwnerID, newRepoName); err != nil {
-		return fmt.Errorf("delete repo redirect: %v", err)
-	}
-
-	if err := NewRepoRedirect(DBContext{sess}, repo.Owner.ID, repo.ID, oldRepoName, newRepoName); err != nil {
+	if err := newRepoRedirect(sess, repo.Owner.ID, repo.ID, oldRepoName, newRepoName); err != nil {
 		return err
 	}
 
diff --git a/models/repo_redirect.go b/models/repo_redirect.go
index 182b6b41a2..afbfeb499e 100644
--- a/models/repo_redirect.go
+++ b/models/repo_redirect.go
@@ -28,16 +28,16 @@ func LookupRepoRedirect(ownerID int64, repoName string) (int64, error) {
 	return redirect.RedirectRepoID, nil
 }
 
-// NewRepoRedirect create a new repo redirect
-func NewRepoRedirect(ctx DBContext, ownerID, repoID int64, oldRepoName, newRepoName string) error {
+// newRepoRedirect create a new repo redirect
+func newRepoRedirect(e Engine, ownerID, repoID int64, oldRepoName, newRepoName string) error {
 	oldRepoName = strings.ToLower(oldRepoName)
 	newRepoName = strings.ToLower(newRepoName)
 
-	if err := deleteRepoRedirect(ctx.e, ownerID, newRepoName); err != nil {
+	if err := deleteRepoRedirect(e, ownerID, newRepoName); err != nil {
 		return err
 	}
 
-	if _, err := ctx.e.Insert(&RepoRedirect{
+	if _, err := e.Insert(&RepoRedirect{
 		OwnerID:        ownerID,
 		LowerName:      oldRepoName,
 		RedirectRepoID: repoID,
diff --git a/models/repo_redirect_test.go b/models/repo_redirect_test.go
index 44ec2b4e94..4c3184a0fd 100644
--- a/models/repo_redirect_test.go
+++ b/models/repo_redirect_test.go
@@ -26,7 +26,7 @@ func TestNewRepoRedirect(t *testing.T) {
 	assert.NoError(t, PrepareTestDatabase())
 
 	repo := AssertExistsAndLoadBean(t, &Repository{ID: 1}).(*Repository)
-	assert.NoError(t, NewRepoRedirect(DefaultDBContext(), repo.OwnerID, repo.ID, repo.Name, "newreponame"))
+	assert.NoError(t, newRepoRedirect(x, repo.OwnerID, repo.ID, repo.Name, "newreponame"))
 
 	AssertExistsAndLoadBean(t, &RepoRedirect{
 		OwnerID:        repo.OwnerID,
@@ -45,7 +45,7 @@ func TestNewRepoRedirect2(t *testing.T) {
 	assert.NoError(t, PrepareTestDatabase())
 
 	repo := AssertExistsAndLoadBean(t, &Repository{ID: 1}).(*Repository)
-	assert.NoError(t, NewRepoRedirect(DefaultDBContext(), repo.OwnerID, repo.ID, repo.Name, "oldrepo1"))
+	assert.NoError(t, newRepoRedirect(x, repo.OwnerID, repo.ID, repo.Name, "oldrepo1"))
 
 	AssertExistsAndLoadBean(t, &RepoRedirect{
 		OwnerID:        repo.OwnerID,
@@ -64,7 +64,7 @@ func TestNewRepoRedirect3(t *testing.T) {
 	assert.NoError(t, PrepareTestDatabase())
 
 	repo := AssertExistsAndLoadBean(t, &Repository{ID: 2}).(*Repository)
-	assert.NoError(t, NewRepoRedirect(DefaultDBContext(), repo.OwnerID, repo.ID, repo.Name, "newreponame"))
+	assert.NoError(t, newRepoRedirect(x, repo.OwnerID, repo.ID, repo.Name, "newreponame"))
 
 	AssertExistsAndLoadBean(t, &RepoRedirect{
 		OwnerID:        repo.OwnerID,
diff --git a/models/user.go b/models/user.go
index 746608aaa4..8147c9f626 100644
--- a/models/user.go
+++ b/models/user.go
@@ -863,6 +863,10 @@ func CreateUser(u *User) (err error) {
 		return ErrUserAlreadyExist{u.Name}
 	}
 
+	if err = deleteUserRedirect(sess, u.Name); err != nil {
+		return err
+	}
+
 	u.Email = strings.ToLower(u.Email)
 	isExist, err = sess.
 		Where("email=?", u.Email).
@@ -973,6 +977,7 @@ func VerifyActiveEmailCode(code, email string) *EmailAddress {
 
 // ChangeUserName changes all corresponding setting from old user name to new one.
 func ChangeUserName(u *User, newUserName string) (err error) {
+	oldUserName := u.Name
 	if err = IsUsableUsername(newUserName); err != nil {
 		return err
 	}
@@ -990,16 +995,28 @@ func ChangeUserName(u *User, newUserName string) (err error) {
 		return ErrUserAlreadyExist{newUserName}
 	}
 
-	if _, err = sess.Exec("UPDATE `repository` SET owner_name=? WHERE owner_name=?", newUserName, u.Name); err != nil {
+	if _, err = sess.Exec("UPDATE `repository` SET owner_name=? WHERE owner_name=?", newUserName, oldUserName); err != nil {
 		return fmt.Errorf("Change repo owner name: %v", err)
 	}
 
 	// Do not fail if directory does not exist
-	if err = os.Rename(UserPath(u.Name), UserPath(newUserName)); err != nil && !os.IsNotExist(err) {
+	if err = os.Rename(UserPath(oldUserName), UserPath(newUserName)); err != nil && !os.IsNotExist(err) {
 		return fmt.Errorf("Rename user directory: %v", err)
 	}
 
-	return sess.Commit()
+	if err = newUserRedirect(sess, u.ID, oldUserName, newUserName); err != nil {
+		return err
+	}
+
+	if err = sess.Commit(); err != nil {
+		if err2 := os.Rename(UserPath(newUserName), UserPath(oldUserName)); err2 != nil && !os.IsNotExist(err2) {
+			log.Critical("Unable to rollback directory change during failed username change from: %s to: %s. DB Error: %v. Filesystem Error: %v", oldUserName, newUserName, err, err2)
+			return fmt.Errorf("failed to rollback directory change during failed username change from: %s to: %s. DB Error: %w. Filesystem Error: %v", oldUserName, newUserName, err, err2)
+		}
+		return err
+	}
+
+	return nil
 }
 
 // checkDupEmail checks whether there are the same email with the user
diff --git a/models/user_redirect.go b/models/user_redirect.go
new file mode 100644
index 0000000000..1da8b44088
--- /dev/null
+++ b/models/user_redirect.go
@@ -0,0 +1,52 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package models
+
+import "strings"
+
+// UserRedirect represents that a user name should be redirected to another
+type UserRedirect struct {
+	ID             int64  `xorm:"pk autoincr"`
+	LowerName      string `xorm:"UNIQUE(s) INDEX NOT NULL"`
+	RedirectUserID int64  // userID to redirect to
+}
+
+// LookupUserRedirect look up userID if a user has a redirect name
+func LookupUserRedirect(userName string) (int64, error) {
+	userName = strings.ToLower(userName)
+	redirect := &UserRedirect{LowerName: userName}
+	if has, err := x.Get(redirect); err != nil {
+		return 0, err
+	} else if !has {
+		return 0, ErrUserRedirectNotExist{Name: userName}
+	}
+	return redirect.RedirectUserID, nil
+}
+
+// newUserRedirect create a new user redirect
+func newUserRedirect(e Engine, ID int64, oldUserName, newUserName string) error {
+	oldUserName = strings.ToLower(oldUserName)
+	newUserName = strings.ToLower(newUserName)
+
+	if err := deleteUserRedirect(e, newUserName); err != nil {
+		return err
+	}
+
+	if _, err := e.Insert(&UserRedirect{
+		LowerName:      oldUserName,
+		RedirectUserID: ID,
+	}); err != nil {
+		return err
+	}
+	return nil
+}
+
+// deleteUserRedirect delete any redirect from the specified user name to
+// anything else
+func deleteUserRedirect(e Engine, userName string) error {
+	userName = strings.ToLower(userName)
+	_, err := e.Delete(&UserRedirect{LowerName: userName})
+	return err
+}
diff --git a/models/user_redirect_test.go b/models/user_redirect_test.go
new file mode 100644
index 0000000000..791c920bcf
--- /dev/null
+++ b/models/user_redirect_test.go
@@ -0,0 +1,69 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package models
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestLookupUserRedirect(t *testing.T) {
+	assert.NoError(t, PrepareTestDatabase())
+
+	userID, err := LookupUserRedirect("olduser1")
+	assert.NoError(t, err)
+	assert.EqualValues(t, 1, userID)
+
+	_, err = LookupUserRedirect("doesnotexist")
+	assert.True(t, IsErrUserRedirectNotExist(err))
+}
+
+func TestNewUserRedirect(t *testing.T) {
+	// redirect to a completely new name
+	assert.NoError(t, PrepareTestDatabase())
+
+	user := AssertExistsAndLoadBean(t, &User{ID: 1}).(*User)
+	assert.NoError(t, newUserRedirect(x, user.ID, user.Name, "newusername"))
+
+	AssertExistsAndLoadBean(t, &UserRedirect{
+		LowerName:      user.LowerName,
+		RedirectUserID: user.ID,
+	})
+	AssertExistsAndLoadBean(t, &UserRedirect{
+		LowerName:      "olduser1",
+		RedirectUserID: user.ID,
+	})
+}
+
+func TestNewUserRedirect2(t *testing.T) {
+	// redirect to previously used name
+	assert.NoError(t, PrepareTestDatabase())
+
+	user := AssertExistsAndLoadBean(t, &User{ID: 1}).(*User)
+	assert.NoError(t, newUserRedirect(x, user.ID, user.Name, "olduser1"))
+
+	AssertExistsAndLoadBean(t, &UserRedirect{
+		LowerName:      user.LowerName,
+		RedirectUserID: user.ID,
+	})
+	AssertNotExistsBean(t, &UserRedirect{
+		LowerName:      "olduser1",
+		RedirectUserID: user.ID,
+	})
+}
+
+func TestNewUserRedirect3(t *testing.T) {
+	// redirect for a previously-unredirected user
+	assert.NoError(t, PrepareTestDatabase())
+
+	user := AssertExistsAndLoadBean(t, &User{ID: 2}).(*User)
+	assert.NoError(t, newUserRedirect(x, user.ID, user.Name, "newusername"))
+
+	AssertExistsAndLoadBean(t, &UserRedirect{
+		LowerName:      user.LowerName,
+		RedirectUserID: user.ID,
+	})
+}
diff --git a/modules/context/context.go b/modules/context/context.go
index 1ee31e0ebb..e4121649ae 100644
--- a/modules/context/context.go
+++ b/modules/context/context.go
@@ -90,6 +90,26 @@ func (ctx *Context) IsUserRepoReaderAny() bool {
 	return ctx.Repo.HasAccess()
 }
 
+// RedirectToUser redirect to a differently-named user
+func RedirectToUser(ctx *Context, userName string, redirectUserID int64) {
+	user, err := models.GetUserByID(redirectUserID)
+	if err != nil {
+		ctx.ServerError("GetUserByID", err)
+		return
+	}
+
+	redirectPath := strings.Replace(
+		ctx.Req.URL.Path,
+		userName,
+		user.Name,
+		1,
+	)
+	if ctx.Req.URL.RawQuery != "" {
+		redirectPath += "?" + ctx.Req.URL.RawQuery
+	}
+	ctx.Redirect(path.Join(setting.AppSubURL, redirectPath))
+}
+
 // HasAPIError returns true if error occurs in form validation.
 func (ctx *Context) HasAPIError() bool {
 	hasErr, ok := ctx.Data["HasError"]
diff --git a/modules/context/org.go b/modules/context/org.go
index 9b87fba9fd..f61a39c666 100644
--- a/modules/context/org.go
+++ b/modules/context/org.go
@@ -54,7 +54,14 @@ func HandleOrgAssignment(ctx *Context, args ...bool) {
 	ctx.Org.Organization, err = models.GetUserByName(orgName)
 	if err != nil {
 		if models.IsErrUserNotExist(err) {
-			ctx.NotFound("GetUserByName", err)
+			redirectUserID, err := models.LookupUserRedirect(orgName)
+			if err == nil {
+				RedirectToUser(ctx, orgName, redirectUserID)
+			} else if models.IsErrUserRedirectNotExist(err) {
+				ctx.NotFound("GetUserByName", err)
+			} else {
+				ctx.ServerError("LookupUserRedirect", err)
+			}
 		} else {
 			ctx.ServerError("GetUserByName", err)
 		}
diff --git a/modules/context/repo.go b/modules/context/repo.go
index 2aee6caca4..63cb02dc06 100644
--- a/modules/context/repo.go
+++ b/modules/context/repo.go
@@ -411,11 +411,18 @@ func RepoAssignment() macaron.Handler {
 			owner, err = models.GetUserByName(userName)
 			if err != nil {
 				if models.IsErrUserNotExist(err) {
-					if ctx.Query("go-get") == "1" {
-						EarlyResponseForGoGetMeta(ctx)
-						return
+					redirectUserID, err := models.LookupUserRedirect(userName)
+					if err == nil {
+						RedirectToUser(ctx, userName, redirectUserID)
+					} else if models.IsErrUserRedirectNotExist(err) {
+						if ctx.Query("go-get") == "1" {
+							EarlyResponseForGoGetMeta(ctx)
+							return
+						}
+						ctx.NotFound("GetUserByName", nil)
+					} else {
+						ctx.ServerError("LookupUserRedirect", err)
 					}
-					ctx.NotFound("GetUserByName", nil)
 				} else {
 					ctx.ServerError("GetUserByName", err)
 				}
diff --git a/options/locale/locale_en-US.ini b/options/locale/locale_en-US.ini
index 770670ec1f..6c9604bf8b 100644
--- a/options/locale/locale_en-US.ini
+++ b/options/locale/locale_en-US.ini
@@ -450,6 +450,7 @@ update_language_not_found = Language '%s' is not available.
 update_profile_success = Your profile has been updated.
 change_username = Your username has been changed.
 change_username_prompt = Note: username changes also change your account URL.
+change_username_redirect_prompt = The old username will redirect until it is claimed.
 continue = Continue
 cancel = Cancel
 language = Language
@@ -1941,6 +1942,7 @@ settings.visibility.private_shortname = Private
 settings.update_settings = Update Settings
 settings.update_setting_success = Organization settings have been updated.
 settings.change_orgname_prompt = Note: changing the organization name also changes the organization's URL.
+settings.change_orgname_redirect_prompt = The old name will redirect until it is claimed.
 settings.update_avatar_success = The organization's avatar has been updated.
 settings.delete = Delete Organization
 settings.delete_account = Delete This Organization
diff --git a/routers/api/v1/api.go b/routers/api/v1/api.go
index 02ad8ab360..876f48ca5c 100644
--- a/routers/api/v1/api.go
+++ b/routers/api/v1/api.go
@@ -134,7 +134,13 @@ func repoAssignment() macaron.Handler {
 			owner, err = models.GetUserByName(userName)
 			if err != nil {
 				if models.IsErrUserNotExist(err) {
-					ctx.NotFound()
+					if redirectUserID, err := models.LookupUserRedirect(userName); err == nil {
+						context.RedirectToUser(ctx.Context, userName, redirectUserID)
+					} else if models.IsErrUserRedirectNotExist(err) {
+						ctx.NotFound("GetUserByName", err)
+					} else {
+						ctx.Error(http.StatusInternalServerError, "LookupUserRedirect", err)
+					}
 				} else {
 					ctx.Error(http.StatusInternalServerError, "GetUserByName", err)
 				}
@@ -393,7 +399,14 @@ func orgAssignment(args ...bool) macaron.Handler {
 			ctx.Org.Organization, err = models.GetOrgByName(ctx.Params(":org"))
 			if err != nil {
 				if models.IsErrOrgNotExist(err) {
-					ctx.NotFound()
+					redirectUserID, err := models.LookupUserRedirect(ctx.Params(":org"))
+					if err == nil {
+						context.RedirectToUser(ctx.Context, ctx.Params(":org"), redirectUserID)
+					} else if models.IsErrUserRedirectNotExist(err) {
+						ctx.NotFound("GetOrgByName", err)
+					} else {
+						ctx.Error(http.StatusInternalServerError, "LookupUserRedirect", err)
+					}
 				} else {
 					ctx.Error(http.StatusInternalServerError, "GetOrgByName", err)
 				}
diff --git a/routers/api/v1/user/helper.go b/routers/api/v1/user/helper.go
new file mode 100644
index 0000000000..fcdac257ed
--- /dev/null
+++ b/routers/api/v1/user/helper.go
@@ -0,0 +1,36 @@
+// Copyright 2021 The Gitea Authors.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package user
+
+import (
+	"net/http"
+
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/context"
+)
+
+// GetUserByParamsName get user by name
+func GetUserByParamsName(ctx *context.APIContext, name string) *models.User {
+	username := ctx.Params(name)
+	user, err := models.GetUserByName(username)
+	if err != nil {
+		if models.IsErrUserNotExist(err) {
+			if redirectUserID, err := models.LookupUserRedirect(username); err == nil {
+				context.RedirectToUser(ctx.Context, username, redirectUserID)
+			} else {
+				ctx.NotFound("GetUserByName", err)
+			}
+		} else {
+			ctx.Error(http.StatusInternalServerError, "GetUserByName", err)
+		}
+		return nil
+	}
+	return user
+}
+
+// GetUserByParams returns user whose name is presented in URL (":username").
+func GetUserByParams(ctx *context.APIContext) *models.User {
+	return GetUserByParamsName(ctx, ":username")
+}
diff --git a/routers/api/v1/user/key.go b/routers/api/v1/user/key.go
index 8069660653..fa16df1836 100644
--- a/routers/api/v1/user/key.go
+++ b/routers/api/v1/user/key.go
@@ -39,25 +39,6 @@ func appendPrivateInformation(apiKey *api.PublicKey, key *models.PublicKey, defa
 	return apiKey, nil
 }
 
-// GetUserByParamsName get user by name
-func GetUserByParamsName(ctx *context.APIContext, name string) *models.User {
-	user, err := models.GetUserByName(ctx.Params(name))
-	if err != nil {
-		if models.IsErrUserNotExist(err) {
-			ctx.NotFound()
-		} else {
-			ctx.Error(http.StatusInternalServerError, "GetUserByName", err)
-		}
-		return nil
-	}
-	return user
-}
-
-// GetUserByParams returns user whose name is presented in URL paramenter.
-func GetUserByParams(ctx *context.APIContext) *models.User {
-	return GetUserByParamsName(ctx, ":username")
-}
-
 func composePublicKeysAPILink() string {
 	return setting.AppURL + "api/v1/user/keys/"
 }
diff --git a/routers/api/v1/user/user.go b/routers/api/v1/user/user.go
index b860219e62..ecc149fe52 100644
--- a/routers/api/v1/user/user.go
+++ b/routers/api/v1/user/user.go
@@ -107,13 +107,8 @@ func GetInfo(ctx *context.APIContext) {
 	//   "404":
 	//     "$ref": "#/responses/notFound"
 
-	u, err := models.GetUserByName(ctx.Params(":username"))
-	if err != nil {
-		if models.IsErrUserNotExist(err) {
-			ctx.NotFound()
-		} else {
-			ctx.Error(http.StatusInternalServerError, "GetUserByName", err)
-		}
+	u := GetUserByParams(ctx)
+	if ctx.Written() {
 		return
 	}
 
@@ -153,14 +148,8 @@ func GetUserHeatmapData(ctx *context.APIContext) {
 	//   "404":
 	//     "$ref": "#/responses/notFound"
 
-	// Get the user to throw an error if it does not exist
-	user, err := models.GetUserByName(ctx.Params(":username"))
-	if err != nil {
-		if models.IsErrUserNotExist(err) {
-			ctx.Status(http.StatusNotFound)
-		} else {
-			ctx.Error(http.StatusInternalServerError, "GetUserByName", err)
-		}
+	user := GetUserByParams(ctx)
+	if ctx.Written() {
 		return
 	}
 
diff --git a/routers/repo/http.go b/routers/repo/http.go
index d4464ec62e..3de45698e8 100644
--- a/routers/repo/http.go
+++ b/routers/repo/http.go
@@ -102,8 +102,15 @@ func HTTP(ctx *context.Context) {
 
 	owner, err := models.GetUserByName(username)
 	if err != nil {
-		log.Error("Attempted access of unknown user from %s", ctx.RemoteAddr())
-		ctx.NotFoundOrServerError("GetUserByName", models.IsErrUserNotExist, err)
+		if models.IsErrUserNotExist(err) {
+			if redirectUserID, err := models.LookupUserRedirect(username); err == nil {
+				context.RedirectToUser(ctx, username, redirectUserID)
+			} else {
+				ctx.NotFound("GetUserByName", err)
+			}
+		} else {
+			ctx.ServerError("GetUserByName", err)
+		}
 		return
 	}
 	if !owner.IsOrganization() && !owner.IsActive {
diff --git a/routers/user/profile.go b/routers/user/profile.go
index bd5b359272..e19407baa7 100644
--- a/routers/user/profile.go
+++ b/routers/user/profile.go
@@ -23,7 +23,11 @@ func GetUserByName(ctx *context.Context, name string) *models.User {
 	user, err := models.GetUserByName(name)
 	if err != nil {
 		if models.IsErrUserNotExist(err) {
-			ctx.NotFound("GetUserByName", nil)
+			if redirectUserID, err := models.LookupUserRedirect(name); err == nil {
+				context.RedirectToUser(ctx, name, redirectUserID)
+			} else {
+				ctx.NotFound("GetUserByName", err)
+			}
 		} else {
 			ctx.ServerError("GetUserByName", err)
 		}
diff --git a/templates/org/settings/options.tmpl b/templates/org/settings/options.tmpl
index 348f8cb533..09bf5e0caa 100644
--- a/templates/org/settings/options.tmpl
+++ b/templates/org/settings/options.tmpl
@@ -13,7 +13,10 @@
 					<form class="ui form" action="{{.Link}}" method="post">
 						{{.CsrfTokenHtml}}
 						<div class="required field {{if .Err_Name}}error{{end}}">
-							<label for="org_name">{{.i18n.Tr "org.org_name_holder"}}<span class="text red hide" id="org-name-change-prompt"> {{.i18n.Tr "org.settings.change_orgname_prompt"}}</span></label>
+							<label for="org_name">{{.i18n.Tr "org.org_name_holder"}}
+								<span class="text red hide" id="org-name-change-prompt"> {{.i18n.Tr "org.settings.change_orgname_prompt"}}</span>
+								<span class="text red hide" id="org-name-change-redirect-prompt"> {{.i18n.Tr "org.settings.change_orgname_redirect_prompt"}}</span>
+							</label>
 							<input id="org_name" name="name" value="{{.Org.Name}}" data-org-name="{{.Org.Name}}" autofocus required>
 						</div>
 						<div class="field {{if .Err_FullName}}error{{end}}">
diff --git a/templates/user/settings/profile.tmpl b/templates/user/settings/profile.tmpl
index 7ec8d2a15f..ee3cc58904 100644
--- a/templates/user/settings/profile.tmpl
+++ b/templates/user/settings/profile.tmpl
@@ -11,7 +11,10 @@
 			<form class="ui form" action="{{.Link}}" method="post">
 				{{.CsrfTokenHtml}}
 				<div class="required field {{if .Err_Name}}error{{end}}">
-					<label for="username">{{.i18n.Tr "username"}}<span class="text red hide" id="name-change-prompt"> {{.i18n.Tr "settings.change_username_prompt"}}</span></label>
+					<label for="username">{{.i18n.Tr "username"}}
+						<span class="text red hide" id="name-change-prompt"> {{.i18n.Tr "settings.change_username_prompt"}}</span>
+						<span class="text red hide" id="name-change-redirect-prompt"> {{.i18n.Tr "settings.change_username_redirect_prompt"}}</span>
+					</label>
 					<input id="username" name="name" value="{{.SignedUser.Name}}" data-name="{{.SignedUser.Name}}" autofocus required {{if not .SignedUser.IsLocal}}disabled{{end}}>
 					{{if not .SignedUser.IsLocal}}
 					<p class="help text blue">{{$.i18n.Tr "settings.password_username_disabled"}}</p>
diff --git a/web_src/js/index.js b/web_src/js/index.js
index 16bb412f09..f5f4841410 100644
--- a/web_src/js/index.js
+++ b/web_src/js/index.js
@@ -1736,10 +1736,13 @@ function initOrganization() {
   if ($('.organization.settings.options').length > 0) {
     $('#org_name').on('keyup', function () {
       const $prompt = $('#org-name-change-prompt');
+      const $prompt_redirect = $('#org-name-change-redirect-prompt');
       if ($(this).val().toString().toLowerCase() !== $(this).data('org-name').toString().toLowerCase()) {
         $prompt.show();
+        $prompt_redirect.show();
       } else {
         $prompt.hide();
+        $prompt_redirect.hide();
       }
     });
   }
@@ -1755,10 +1758,13 @@ function initUserSettings() {
   if ($('.user.settings.profile').length > 0) {
     $('#username').on('keyup', function () {
       const $prompt = $('#name-change-prompt');
+      const $prompt_redirect = $('#name-change-redirect-prompt');
       if ($(this).val().toString().toLowerCase() !== $(this).data('name').toString().toLowerCase()) {
         $prompt.show();
+        $prompt_redirect.show();
       } else {
         $prompt.hide();
+        $prompt_redirect.hide();
       }
     });
   }