[BRANDING] alias {FORGEJO,GITEA}_{CUSTOM,WORK_DIR}

FORGEJO_* environment variables are set to the corresponding GITEA_*
variable when the cli starts. This approach is intended to minimize
the conflicts on rebase. All occurences of GITEA_* are left untouched
in the codebase and they are only changed to FORGEJO_* if exposed to
the user.

(cherry picked from commit e466f9d10e)
(cherry picked from commit e33e95931b)
(cherry picked from commit 2cfc6519b7)
(cherry picked from commit af8864373a)
(cherry picked from commit a0550ff339)
(cherry picked from commit 24dc0a5191)
(cherry picked from commit e255eea2b4)
(cherry picked from commit 0c4f5afa7a)
(cherry picked from commit 42fce708d0)
(cherry picked from commit e7278c3c22)
(cherry picked from commit 0fb9ed7e0e)
(cherry picked from commit a98308aa4d)
(cherry picked from commit b8695fcbe0)
(cherry picked from commit 4aee8719f5)
(cherry picked from commit 1c503c1ba7)
(cherry picked from commit cf1ed8551e)
(cherry picked from commit c52459b088)
(cherry picked from commit 92cac277b2)
(cherry picked from commit 2c744f1118)
(cherry picked from commit 989a98a8c5)
(cherry picked from commit 9cf7052bd4)
(cherry picked from commit a13c9667e0)

Conflicts:
	main.go
	https://codeberg.org/forgejo/forgejo/pulls/1216
(cherry picked from commit a9c3cf060d)
(cherry picked from commit eb6d904b23)
(cherry picked from commit fd4878e487)
(cherry picked from commit cc2cab9241)
(cherry picked from commit be523c63db)
(cherry picked from commit 254d1a2f9a)
(cherry picked from commit 1eecf4200e)
(cherry picked from commit a01f5c3475)
(cherry picked from commit b1ba7ce321)
(cherry picked from commit eddfd96beb)
(cherry picked from commit 7a780758c2)
(cherry picked from commit afb88332dc)
(cherry picked from commit af0448d000)
(cherry picked from commit bdfdc7e169)

main.go

@@ -40,7 +40,16 @@ func init() {
 	setting.AppStartTime = time.Now().UTC()
 }
 
+func forgejoEnv() {
+	for _, k := range []string{"CUSTOM", "WORK_DIR"} {
+		if v, ok := os.LookupEnv("FORGEJO_" + k); ok {
+			os.Setenv("GITEA_"+k, v)
+		}
+	}
+}
+
 func main() {
+	forgejoEnv()
 	cli.OsExiter = func(code int) {
 		log.GetManager().Close()
 		os.Exit(code)