Use proxy for pull mirror (#22771)

- Use the proxy (if one is specified) for pull mirrors syncs.
- Pulled the code from
c2774d9e80/modules/git/repo.go (L164-L170)

Downstream issue: https://codeberg.org/forgejo/forgejo/issues/302

---------

Co-authored-by: Lauris BH <lauris@nix.lv>

modules/git/repo.go

@@ -163,10 +163,8 @@ func CloneWithArgs(ctx context.Context, args TrustedCmdArgs, from, to string, op
 
 	envs := os.Environ()
 	u, err := url.Parse(from)
-	if err == nil && (strings.EqualFold(u.Scheme, "http") || strings.EqualFold(u.Scheme, "https")) {
-		if proxy.Match(u.Host) {
-			envs = append(envs, fmt.Sprintf("https_proxy=%s", proxy.GetProxyURL()))
-		}
+	if err == nil {
+		envs = proxy.EnvWithProxy(u)
 	}
 
 	stderr := new(bytes.Buffer)

modules/proxy/proxy.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"strings"
 	"sync"
 
 	"code.gitea.io/gitea/modules/log"
@@ -82,3 +83,16 @@ func Proxy() func(req *http.Request) (*url.URL, error) {
 		return http.ProxyFromEnvironment(req)
 	}
 }
+
+// EnvWithProxy returns os.Environ(), with a https_proxy env, if the given url
+// needs to be proxied.
+func EnvWithProxy(u *url.URL) []string {
+	envs := os.Environ()
+	if strings.EqualFold(u.Scheme, "http") || strings.EqualFold(u.Scheme, "https") {
+		if Match(u.Host) {
+			envs = append(envs, "https_proxy="+GetProxyURL())
+		}
+	}
+
+	return envs
+}