Add flag to always authenticate when cloning public repositories (#760)

As a developer using an custom git server (e.g. Github Enterprise) I would like to be able to authenticate 
the user on repositories which are marked as public.

See issue: https://github.com/woodpecker-ci/woodpecker/issues/473

Ref: https://github.com/woodpecker-ci/woodpecker/pull/693#issuecomment-1025771162

cmd/server/flags.go

@@ -91,6 +91,11 @@ var flags = []cli.Flag{
 		Name:    "open",
 		Usage:   "enable open user registration",
 	},
+	&cli.BoolFlag{
+		EnvVars: []string{"WOODPECKER_AUTHENTICATE_PUBLIC_REPOS"},
+		Name:    "authenticate-public-repos",
+		Usage:   "Always use authentication to clone repositories even if they are public. Needed if the SCM requires to always authenticate as used by many companies.",
+	},
 	&cli.StringFlag{
 		EnvVars: []string{"WOODPECKER_DOCS"},
 		Name:    "docs",

cmd/server/server.go

@@ -271,6 +271,9 @@ func setupEvilGlobals(c *cli.Context, v store.Store, r remote.Remote) {
 		server.Config.Services.Senders = sender.NewRemote(endpoint)
 	}
 
+	// authentication
+	server.Config.Pipeline.AuthenticatePublicRepos = c.Bool("authenticate-public-repos")
+
 	// limits
 	server.Config.Pipeline.Limits.MemSwapLimit = c.Int64("limit-mem-swap")
 	server.Config.Pipeline.Limits.MemLimit = c.Int64("limit-mem")