Auto-subscribe user to repository when they commit/tag to it (#7657)

* Add support for AUTO_WATCH_ON_CHANGES and AUTO_WATCH_ON_CLONE

* Update models/repo_watch.go

Co-Authored-By: Lauris BH <lauris@nix.lv>

* Round up changes suggested by lafriks

* Added changes suggested from automated tests

* Updated deleteUser to take RepoWatchModeDont into account, corrected inverted DefaultWatchOnClone and DefaultWatchOnChanges behaviour, updated and added tests.

* Reinsert import "github.com/Unknwon/com" on http.go

* Add migration for new column `watch`.`mode`

* Remove serv code

* Remove WATCH_ON_CLONE; use hooks, add integrations

* Renamed watch_test.go to repo_watch_test.go

* Correct fmt

* Add missing EOL

* Correct name of test function

* Reword cheat and ini descriptions

* Add update to migration to ensure column value

* Clarify comment

Co-Authored-By: zeripath <art27@cantab.net>

* Simplify if condition

modules/setting/service.go

@@ -44,6 +44,7 @@ var Service struct {
 	NoReplyAddress                          string
 	EnableUserHeatmap                       bool
 	AutoWatchNewRepos                       bool
+	AutoWatchOnChanges                      bool
 	DefaultOrgMemberVisible                 bool
 
 	// OpenID settings
@@ -85,6 +86,7 @@ func newService() {
 	Service.NoReplyAddress = sec.Key("NO_REPLY_ADDRESS").MustString("noreply.example.org")
 	Service.EnableUserHeatmap = sec.Key("ENABLE_USER_HEATMAP").MustBool(true)
 	Service.AutoWatchNewRepos = sec.Key("AUTO_WATCH_NEW_REPOS").MustBool(true)
+	Service.AutoWatchOnChanges = sec.Key("AUTO_WATCH_ON_CHANGES").MustBool(false)
 	Service.DefaultOrgVisibility = sec.Key("DEFAULT_ORG_VISIBILITY").In("public", structs.ExtractKeysFromMapString(structs.VisibilityModes))
 	Service.DefaultOrgVisibilityMode = structs.VisibilityModes[Service.DefaultOrgVisibility]
 	Service.DefaultOrgMemberVisible = sec.Key("DEFAULT_ORG_MEMBER_VISIBLE").MustBool()