conf: overhaul server settings (#5928)

* conf: rename package

* Requires Go 1.12

* Fix lint

* Fix lint

* Overhaul

* db: fix tests

* Save my work

* Fix tests

* Server.UnixSocketPermission

* Server.LocalRootURL

* SSH settings

* Server.OfflineMode

* Save my work

* App.Version

* Remove [server] STATIC_ROOT_PATH

* Server.LandingURL

internal/conf/computed.go

@@ -0,0 +1,116 @@
+// Copyright 2020 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package conf
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+)
+
+// ℹ️ README: This file contains configuration values that require computation to be useful.
+
+// IsWindowsRuntime returns true if the current runtime in Windows.
+func IsWindowsRuntime() bool {
+	return runtime.GOOS == "windows"
+}
+
+// IsProdMode returns true if the application is running in production mode.
+func IsProdMode() bool {
+	return strings.EqualFold(App.RunMode, "prod")
+}
+
+var (
+	appPath     string
+	appPathOnce sync.Once
+)
+
+// AppPath returns the absolute path of the application's binary.
+func AppPath() string {
+	appPathOnce.Do(func() {
+		var err error
+		appPath, err = exec.LookPath(os.Args[0])
+		if err != nil {
+			panic("look executable path: " + err.Error())
+		}
+
+		appPath, err = filepath.Abs(appPath)
+		if err != nil {
+			panic("get absolute executable path: " + err.Error())
+		}
+	})
+
+	return appPath
+}
+
+var (
+	workDir     string
+	workDirOnce sync.Once
+)
+
+// WorkDir returns the absolute path of work directory. It reads the value of envrionment
+// variable GOGS_WORK_DIR. When not set, it uses the directory where the application's
+// binary is located.
+func WorkDir() string {
+	workDirOnce.Do(func() {
+		workDir = os.Getenv("GOGS_WORK_DIR")
+		if workDir != "" {
+			return
+		}
+
+		workDir = filepath.Dir(AppPath())
+	})
+
+	return workDir
+}
+
+var (
+	customDir     string
+	customDirOnce sync.Once
+)
+
+// CustomDir returns the absolute path of the custom directory that contains local overrides.
+// It reads the value of envrionment variable GOGS_CUSTOM. When not set, it uses the work
+// directory returned by WorkDir fucntion.
+func CustomDir() string {
+	customDirOnce.Do(func() {
+		customDir = os.Getenv("GOGS_CUSTOM")
+		if customDir != "" {
+			return
+		}
+
+		customDir = filepath.Join(WorkDir(), "custom")
+	})
+
+	return customDir
+}
+
+var (
+	homeDir     string
+	homeDirOnce sync.Once
+)
+
+// HomeDir returns the home directory by reading environment variables. It may return empty
+// string when environment variables are not set.
+func HomeDir() string {
+	homeDirOnce.Do(func() {
+		if !IsWindowsRuntime() {
+			homeDir = os.Getenv("HOME")
+			return
+		}
+
+		homeDir = os.Getenv("USERPROFILE")
+		if homeDir != "" {
+			return
+		}
+
+		homeDir = os.Getenv("HOMEDRIVE") + os.Getenv("HOMEPATH")
+	})
+
+	return homeDir
+}