Add more test directory to exclude dir of air, remove watching templates from air include dir because gitea has internal mechanism (#22246)

Since #20218 introduced internal watching template, template watching
should be removed from `air`. This will prevent restart the whole server
once the template files changed to speed up developing when using `make
watch`.

To ensure `make watch` will reuse template watching, this PR introduced
a new ENV `GITEA_RUN_MODE` to make sure `make watch` will always run in
a dev mode of Gitea so that template watching will open.

This PR also added more exclude testdata directories.

.air.toml

@@ -5,6 +5,6 @@ tmp_dir = ".air"
 cmd = "make backend"
 bin = "gitea"
 include_ext = ["go", "tmpl"]
-exclude_dir = ["modules/git/tests", "services/gitdiff/testdata", "modules/avatar/testdata"]
-include_dir = ["cmd", "models", "modules", "options", "routers", "services", "templates"]
+exclude_dir = ["modules/git/tests", "services/gitdiff/testdata", "modules/avatar/testdata", "models/fixtures", "models/migrations/fixtures", "modules/migration/file_format_testdata", "modules/avatar/identicon/testdata"]
+include_dir = ["cmd", "models", "modules", "options", "routers", "services"]
 exclude_regex = ["_test.go$", "_gen.go$"]

Makefile

@@ -359,7 +359,7 @@ watch-frontend: node-check node_modules
 
 .PHONY: watch-backend
 watch-backend: go-check
-	$(GO) run $(AIR_PACKAGE) -c .air.toml
+	GITEA_RUN_MODE=dev $(GO) run $(AIR_PACKAGE) -c .air.toml
 
 .PHONY: test
 test: test-frontend test-backend

modules/setting/setting.go

@@ -1043,7 +1043,10 @@ func loadFromConf(allowEmpty bool, extraConfig string) {
 	// The following is a purposefully undocumented option. Please do not run Gitea as root. It will only cause future headaches.
 	// Please don't use root as a bandaid to "fix" something that is broken, instead the broken thing should instead be fixed properly.
 	unsafeAllowRunAsRoot := Cfg.Section("").Key("I_AM_BEING_UNSAFE_RUNNING_AS_ROOT").MustBool(false)
+	RunMode = os.Getenv("GITEA_RUN_MODE")
+	if RunMode == "" {
 		RunMode = Cfg.Section("").Key("RUN_MODE").MustString("prod")
+	}
 	IsProd = strings.EqualFold(RunMode, "prod")
 	// Does not check run user when the install lock is off.
 	if InstallLock {