refactor: improve code quality and efficiency in various files (#548)

- Replace loadConfig() with _ = loadConfig()
- Update file permissions from 0660 to 0o660
- Simplify variable declarations
- Replace golang.org/x/crypto/ssh/terminal with golang.org/x/term
- Remove unused getCertPrincipals function
- Replace time.Now().Sub() with time.Since()
- Add test for ArgToIndex function

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/gitea/tea/pulls/548
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: techknowlogick <techknowlogick@noreply.gitea.io>
Co-authored-by: appleboy <appleboy.tw@gmail.com>
Co-committed-by: appleboy <appleboy.tw@gmail.com>

modules/print/repo.go

@@ -14,7 +14,7 @@ import (
 
 // ReposList prints a listing of the repos
 func ReposList(repos []*gitea.Repository, output string, fields []string) {
-	var printables = make([]printable, len(repos))
+	printables := make([]printable, len(repos))
 	for i, r := range repos {
 		printables[i] = &printableRepo{r}
 	}
@@ -56,7 +56,7 @@ func RepoDetails(repo *gitea.Repository, topics []string) {
 	updated := fmt.Sprintf(
 		"Updated: %s (%s ago)\n",
 		repo.Updated.Format("2006-01-02 15:04"),
-		time.Now().Sub(repo.Updated).Truncate(time.Minute),
+		time.Since(repo.Updated).Truncate(time.Minute),
 	)
 
 	urls := fmt.Sprintf(