Support path prefix (#1714)

closes #1636 
closes #1429
supersedes #1586

Uses a different approach: just take the index.html compiled by vite and
replace the paths to js and other files using regex. This is not
compatible with the dev proxy which is also the reason why we can't use
go templates for this.

cmd/server/flags.go

@@ -45,6 +45,11 @@ var flags = []cli.Flag{
 		Name:    "server-host",
 		Usage:   "server fully qualified url (<scheme>://<host>)",
 	},
+	&cli.StringFlag{
+		EnvVars: []string{"WOODPECKER_ROOT_URL"},
+		Name:    "root-url",
+		Usage:   "server url root (used for statics loading when having a url path prefix)",
+	},
 	&cli.StringFlag{
 		EnvVars: []string{"WOODPECKER_SERVER_ADDR"},
 		Name:    "server-addr",

cmd/server/server.go

@@ -354,6 +354,7 @@ func setupEvilGlobals(c *cli.Context, v store.Store, f forge.Forge) {
 	server.Config.Server.StatusContext = c.String("status-context")
 	server.Config.Server.StatusContextFormat = c.String("status-context-format")
 	server.Config.Server.SessionExpires = c.Duration("session-expires")
+	server.Config.Server.RootURL = strings.TrimSuffix(c.String("root-url"), "/")
 	server.Config.Pipeline.Networks = c.StringSlice("network")
 	server.Config.Pipeline.Volumes = c.StringSlice("volume")
 	server.Config.Pipeline.Privileged = c.StringSlice("escalate")