fix: classify git failures on stderr, restrict migration failure detail (#39010)

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/migrate/codebase.tmpl

@@ -19,11 +19,11 @@
 					</span>
 				</div>
 
-				<div class="inline field {{if .Err_Auth}}error{{end}}">
+				<div class="inline field">
 					<label for="auth_username">{{ctx.Locale.Tr "username"}}</label>
 					<input id="auth_username" name="auth_username" value="{{.auth_username}}" {{if not .auth_username}}data-need-clear="true"{{end}}>
 				</div>
-				<div class="inline field {{if .Err_Auth}}error{{end}}">
+				<div class="inline field">
 					<label for="auth_password">{{ctx.Locale.Tr "password"}}</label>
 					<input id="auth_password" name="auth_password" type="password" value="{{.auth_password}}">
 				</div>