refactor: drop logrus and other direct dependencies (#1319)

After https://gitea.com/gitea/runner/pulls/1304, logrus stayed only to forward logs from docker/cli and moby/go-archive. The runner used a small part of those: volume parsing, the build context tar, the `ssh://` connection and registry credentials. Own code that matches them replaces them, so logrus leaves the module graph. docker/cli stays for its logrus-free `opts` and `connhelper/ssh` packages.

Other dependencies that the standard library or existing ones cover go too: mergo, httprouter (replaced by `http.ServeMux`), retry-go, go-isatty, go-selinux, container-device-interface, gotest.tools and go-cmp (replaced by testify). The binary shrinks by 5%.

Behaviour differences:

1. An unreadable file in a build context is skipped with a warning, where go-archive left a truncated tar.
2. Build contexts no longer carry `security.capability` xattrs.
3. The cache and artifact servers answer HEAD on GET routes, and no longer redirect trailing slashes or answer OPTIONS.

*Written by Claude.*

---------

Co-authored-by: bircni <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1319
Reviewed-by: bircni <[email protected]>
Reviewed-by: Lunny Xiao <[email protected]>
Co-authored-by: silverwind <[email protected]>

act/container/docker_ssh_test.go

@@ -0,0 +1,51 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+//go:build !(WITHOUT_DOCKER || !(linux || darwin || windows || netbsd))
+
+package container
+
+import (
+	"io"
+	"os/exec"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSSHArgs(t *testing.T) {
+	args, err := sshArgs("ssh://me@host:2222/run/user/1000/my docker.sock")
+	require.NoError(t, err)
+	assert.Equal(t, []string{"-l", "me", "-p", "2222", "-o", "ConnectTimeout=30", "-T", "--", "host", "docker '--host=unix:///run/user/1000/my docker.sock' system dial-stdio"}, args)
+
+	args, err = sshArgs("ssh://[::1]")
+	require.NoError(t, err)
+	assert.Equal(t, []string{"-o", "ConnectTimeout=30", "-T", "--", "::1", "docker system dial-stdio"}, args)
+
+	for _, invalid := range []string{"ssh://me:secret@host", "ssh://host?x=1", "ssh://host#x", "ssh://"} {
+		_, err := sshArgs(invalid)
+		assert.Error(t, err, invalid)
+	}
+}
+
+func TestDialCommandStreamsStdioAndReportsExit(t *testing.T) {
+	if _, err := exec.LookPath("sh"); err != nil {
+		t.Skip("needs a POSIX shell")
+	}
+	conn, err := dialCommand("sh", "-c", "cat")
+	require.NoError(t, err)
+	_, err = conn.Write([]byte("ping"))
+	require.NoError(t, err)
+	require.NoError(t, conn.(interface{ CloseWrite() error }).CloseWrite())
+	echoed, err := io.ReadAll(conn)
+	require.NoError(t, err)
+	assert.Equal(t, "ping", string(echoed))
+	require.NoError(t, conn.Close())
+
+	conn, err = dialCommand("sh", "-c", "exec 3<&0; cat <&3 >/dev/null & echo 'no route to host' >&2; exit 255")
+	require.NoError(t, err)
+	_, err = io.ReadAll(conn)
+	require.ErrorContains(t, err, "no route to host")
+	require.NoError(t, conn.Close())
+}