transport: ssh, fix cloning large repositories (#272)

* Fix cloning large repositories

Ignore the error on close when the connection is already closed

Fixes #70

* Compatibility for go 1.13

Because it's required by the pipeline

* Add test for allowing to close a command when the client is already closed

This test is for issue #70

* Add debug information for broken test

2 files changed, 29 insertions, 1 deletions

diff --git a/plumbing/transport/ssh/common.go b/plumbing/transport/ssh/common.go
index c05ded9..46e7913 100644
--- a/plumbing/transport/ssh/common.go
+++ b/plumbing/transport/ssh/common.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"reflect"
 	"strconv"
+	"strings"
 
 	"github.com/go-git/go-git/v5/plumbing/transport"
 	"github.com/go-git/go-git/v5/plumbing/transport/internal/common"
@@ -90,8 +91,14 @@ func (c *command) Close() error {
 	//XXX: If did read the full packfile, then the session might be already
 	//     closed.
 	_ = c.Session.Close()
+	err := c.client.Close()
 
-	return c.client.Close()
+	//XXX: in go1.16+ we can use errors.Is(err, net.ErrClosed)
+	if err != nil && strings.HasSuffix(err.Error(), "use of closed network connection") {
+		return nil
+	}
+
+	return err
 }
 
 // connect connects to the SSH server, unless a AuthMethod was set with
diff --git a/plumbing/transport/ssh/common_test.go b/plumbing/transport/ssh/common_test.go
index 87c1148..e04a9c5 100644
--- a/plumbing/transport/ssh/common_test.go
+++ b/plumbing/transport/ssh/common_test.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/kevinburke/ssh_config"
 	"golang.org/x/crypto/ssh"
+	stdssh "golang.org/x/crypto/ssh"
 	. "gopkg.in/check.v1"
 )
 
@@ -93,6 +94,26 @@ func (s *SuiteCommon) TestDefaultSSHConfigWildcard(c *C) {
 	c.Assert(cmd.getHostWithPort(), Equals, "github.com:22")
 }
 
+func (s *SuiteCommon) TestIssue70(c *C) {
+	uploadPack := &UploadPackSuite{}
+	uploadPack.SetUpSuite(c)
+
+	config := &ssh.ClientConfig{
+		HostKeyCallback: stdssh.InsecureIgnoreHostKey(),
+	}
+	r := &runner{
+		config: config,
+	}
+
+	cmd, err := r.Command("command", uploadPack.newEndpoint(c, "endpoint"), uploadPack.EmptyAuth)
+	c.Assert(err, IsNil)
+
+	c.Assert(cmd.(*command).client.Close(), IsNil)
+
+	err = cmd.Close()
+	c.Assert(err, IsNil)
+}
+
 type mockSSHConfig struct {
 	Values map[string]map[string]string
 }