Refactor to use urfave/cli/v2 (#25959)

Replace #10912

And there are many new tests to cover the CLI behavior

There were some concerns about the "option order in hook scripts"
(https://github.com/go-gitea/gitea/pull/10912#issuecomment-1137543314),
it's not a problem now. Because the hook script uses `/gitea hook
--config=/app.ini pre-receive` format. The "config" is a global option,
it can appear anywhere.

----

## ⚠️ BREAKING ⚠️

This PR does it best to avoid breaking anything. The major changes are:

* `gitea` itself won't accept web's options: `--install-port` / `--pid`
/ `--port` / `--quiet` / `--verbose` .... They are `web` sub-command's
options.
    * Use `./gitea web --pid ....` instead
* `./gitea` can still run the `web` sub-command as shorthand, with
default options
* The sub-command's options must follow the sub-command
* Before: `./gitea --sub-opt subcmd` might equal to `./gitea subcmd
--sub-opt` (well, might not ...)
    * After: only `./gitea subcmd --sub-opt` could be used
    * The global options like `--config` are not affected

cmd/main_test.go

@@ -4,9 +4,17 @@
 package cmd
 
 import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 
 	"code.gitea.io/gitea/models/unittest"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/urfave/cli/v2"
 )
 
 func TestMain(m *testing.M) {
@@ -14,3 +22,110 @@ func TestMain(m *testing.M) {
 		GiteaRootPath: "..",
 	})
 }
+
+func makePathOutput(workPath, customPath, customConf string) string {
+	return fmt.Sprintf("WorkPath=%s\nCustomPath=%s\nCustomConf=%s", workPath, customPath, customConf)
+}
+
+func newTestApp() *cli.App {
+	app := NewMainApp()
+	testCmd := &cli.Command{
+		Name: "test-cmd",
+		Action: func(ctx *cli.Context) error {
+			_, _ = fmt.Fprint(app.Writer, makePathOutput(setting.AppWorkPath, setting.CustomPath, setting.CustomConf))
+			return nil
+		},
+	}
+	prepareSubcommandWithConfig(testCmd, appGlobalFlags())
+	app.Commands = append(app.Commands, testCmd)
+	app.DefaultCommand = testCmd.Name
+	return app
+}
+
+func TestCliCmd(t *testing.T) {
+	defaultWorkPath := filepath.Dir(setting.AppPath)
+	defaultCustomPath := filepath.Join(defaultWorkPath, "custom")
+	defaultCustomConf := filepath.Join(defaultCustomPath, "conf/app.ini")
+
+	cli.CommandHelpTemplate = "(command help template)"
+	cli.AppHelpTemplate = "(app help template)"
+	cli.SubcommandHelpTemplate = "(subcommand help template)"
+
+	cases := []struct {
+		env map[string]string
+		cmd string
+		exp string
+	}{
+		// main command help
+		{
+			cmd: "./gitea help",
+			exp: "DEFAULT CONFIGURATION:",
+		},
+
+		// parse paths
+		{
+			cmd: "./gitea test-cmd",
+			exp: makePathOutput(defaultWorkPath, defaultCustomPath, defaultCustomConf),
+		},
+		{
+			cmd: "./gitea -c /tmp/app.ini test-cmd",
+			exp: makePathOutput(defaultWorkPath, defaultCustomPath, "/tmp/app.ini"),
+		},
+		{
+			cmd: "./gitea test-cmd -c /tmp/app.ini",
+			exp: makePathOutput(defaultWorkPath, defaultCustomPath, "/tmp/app.ini"),
+		},
+		{
+			env: map[string]string{"GITEA_WORK_DIR": "/tmp"},
+			cmd: "./gitea test-cmd",
+			exp: makePathOutput("/tmp", "/tmp/custom", "/tmp/custom/conf/app.ini"),
+		},
+		{
+			env: map[string]string{"GITEA_WORK_DIR": "/tmp"},
+			cmd: "./gitea test-cmd --work-path /tmp/other",
+			exp: makePathOutput("/tmp/other", "/tmp/other/custom", "/tmp/other/custom/conf/app.ini"),
+		},
+		{
+			env: map[string]string{"GITEA_WORK_DIR": "/tmp"},
+			cmd: "./gitea test-cmd --config /tmp/app-other.ini",
+			exp: makePathOutput("/tmp", "/tmp/custom", "/tmp/app-other.ini"),
+		},
+	}
+
+	app := newTestApp()
+	var envBackup []string
+	for _, s := range os.Environ() {
+		if strings.HasPrefix(s, "GITEA_") && strings.Contains(s, "=") {
+			envBackup = append(envBackup, s)
+		}
+	}
+	clearGiteaEnv := func() {
+		for _, s := range os.Environ() {
+			if strings.HasPrefix(s, "GITEA_") {
+				_ = os.Unsetenv(s)
+			}
+		}
+	}
+	defer func() {
+		clearGiteaEnv()
+		for _, s := range envBackup {
+			k, v, _ := strings.Cut(s, "=")
+			_ = os.Setenv(k, v)
+		}
+	}()
+
+	for _, c := range cases {
+		clearGiteaEnv()
+		for k, v := range c.env {
+			_ = os.Setenv(k, v)
+		}
+		args := strings.Split(c.cmd, " ") // for test only, "split" is good enough
+		out := new(strings.Builder)
+		app.Writer = out
+		err := app.Run(args)
+		assert.NoError(t, err, c.cmd)
+		assert.NotEmpty(t, c.exp, c.cmd)
+		outStr := out.String()
+		assert.Contains(t, outStr, c.exp, c.cmd)
+	}
+}