Merge pull request #335 from tonistiigi/git-cancellation

git: fix cancellation on blocking remotes

source/git/gitsource.go

@@ -374,13 +374,15 @@ func git(ctx context.Context, dir string, args ...string) (*bytes.Buffer, error)
 		stdout, stderr := logs.NewLogStreams(ctx)
 		defer stdout.Close()
 		defer stderr.Close()
-		cmd := exec.CommandContext(ctx, "git", args...)
+		cmd := exec.Command("git", args...)
 		cmd.Dir = dir // some commands like submodule require this
 		buf := bytes.NewBuffer(nil)
 		errbuf := bytes.NewBuffer(nil)
 		cmd.Stdout = io.MultiWriter(stdout, buf)
 		cmd.Stderr = io.MultiWriter(stderr, errbuf)
-		err := cmd.Run()
+		// remote git commands spawn helper processes that inherit FDs and don't
+		// handle parent death signal so exec.CommandContext can't be used
+		err := runProcessGroup(ctx, cmd)
 		if err != nil {
 			if strings.Contains(errbuf.String(), "--depth") || strings.Contains(errbuf.String(), "shallow") {
 				if newArgs := argsNoDepth(args); len(args) > len(newArgs) {

source/git/gitsource_unix.go

@@ -0,0 +1,27 @@
+// +build !windows
+
+package git
+
+import (
+	"context"
+	"os/exec"
+	"syscall"
+)
+
+func runProcessGroup(ctx context.Context, cmd *exec.Cmd) error {
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+	waitDone := make(chan struct{})
+	go func() {
+		select {
+		case <-ctx.Done():
+			syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
+		case <-waitDone:
+		}
+	}()
+	err := cmd.Wait()
+	close(waitDone)
+	return err
+}

source/git/gitsource_windows.go

@@ -0,0 +1,23 @@
+// +build windows
+
+package git
+
+import (
+	"context"
+	"os/exec"
+)
+
+func runProcessGroup(ctx context.Context, cmd *exec.Cmd) error {
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+	waitDone := make(chan struct{})
+	go func() {
+		select {
+		case <-ctx.Done():
+			cmd.Process.Kill()
+		case <-waitDone:
+		}
+	}()
+	return cmd.Wait()
+}