Prevent zombie processes (#16314)

Unfortunately go doesn't always ensure that execd processes are completely
waited for. On linux this means that zombie processes can occur.

This PR ensures that these are waited for by using signal notifier in serv and
passing a context elsewhere.

Signed-off-by: Andrew Thornton <art27@cantab.net>

cmd/serv.go

@@ -6,14 +6,17 @@
 package cmd
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 	"net/url"
 	"os"
 	"os/exec"
+	"os/signal"
 	"regexp"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 
 	"code.gitea.io/gitea/models"
@@ -273,12 +276,31 @@ func runServ(c *cli.Context) error {
 		verb = strings.Replace(verb, "-", " ", 1)
 	}
 
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go func() {
+		// install notify
+		signalChannel := make(chan os.Signal, 1)
+
+		signal.Notify(
+			signalChannel,
+			syscall.SIGINT,
+			syscall.SIGTERM,
+		)
+		select {
+		case <-signalChannel:
+		case <-ctx.Done():
+		}
+		cancel()
+		signal.Reset()
+	}()
+
 	var gitcmd *exec.Cmd
 	verbs := strings.Split(verb, " ")
 	if len(verbs) == 2 {
-		gitcmd = exec.Command(verbs[0], verbs[1], repoPath)
+		gitcmd = exec.CommandContext(ctx, verbs[0], verbs[1], repoPath)
 	} else {
-		gitcmd = exec.Command(verb, repoPath)
+		gitcmd = exec.CommandContext(ctx, verb, repoPath)
 	}
 
 	gitcmd.Dir = setting.RepoRootPath