Use golangci-lint fmt to format code (#163)

Use `golangci-lint fmt` to format code, upgrading `.golangci.yml` to v2 and mirroring the linter configuration used by https://github.com/go-gitea/gitea. `gci` now handles import ordering into standard, project-local, blank, and default groups.

Mirrors https://github.com/go-gitea/gitea/pull/37194.

Changes:
- Upgrade `.golangci.yml` to v2 format with the same linter set as gitea (minus `prealloc`, `unparam`, `testifylint`, `nilnil` which produced too many pre-existing issues)
- Add path-based exclusions (`bodyclose`, `gosec` in tests; `gosec:G115`/`G117` globally)
- Run lint via `make lint-go` in CI instead of `golangci/golangci-lint-action`, matching the pattern used by other Gitea repos
- Apply safe auto-fixes (`modernize`, `perfsprint`, `usetesting`, etc.)
- Add explanations to existing `//nolint` directives
- Remove dead code (unused `newRemoteReusableWorkflow` and `networkName`), duplicate imports, and shadowed `max` builtins
- Replace deprecated `docker/distribution/reference` with `distribution/reference`
- Fix `Deprecated:` comment casing and simplify nil/len checks

---
This PR was written with the help of Claude Opus 4.7

Reviewed-on: https://gitea.com/gitea/act/pulls/163
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

cmd/notices.go

@@ -76,7 +76,7 @@ func getVersionNotices(version string) []Notice {
 	noticeURL.RawQuery = query.Encode()
 
 	client := &http.Client{}
-	req, err := http.NewRequest("GET", noticeURL.String(), nil)
+	req, err := http.NewRequest(http.MethodGet, noticeURL.String(), nil)
 	if err != nil {
 		log.Debug(err)
 		return nil
@@ -102,7 +102,7 @@ func getVersionNotices(version string) []Notice {
 
 	defer resp.Body.Close()
 	notices := []Notice{}
-	if resp.StatusCode == 304 {
+	if resp.StatusCode == http.StatusNotModified {
 		log.Debug("No new notices")
 		return nil
 	}

cmd/root.go

@@ -4,13 +4,22 @@ import (
 	"bufio"
 	"context"
 	"fmt"
+	"maps"
 	"os"
 	"path/filepath"
 	"regexp"
 	"runtime"
 	"runtime/debug"
+	"strconv"
 	"strings"
 
+	"github.com/nektos/act/pkg/artifactcache"
+	"github.com/nektos/act/pkg/artifacts"
+	"github.com/nektos/act/pkg/common"
+	"github.com/nektos/act/pkg/container"
+	"github.com/nektos/act/pkg/model"
+	"github.com/nektos/act/pkg/runner"
+
 	"github.com/AlecAivazis/survey/v2"
 	"github.com/adrg/xdg"
 	"github.com/andreaskoch/go-fswatch"
@@ -20,13 +29,6 @@ import (
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	"go.yaml.in/yaml/v4"
-
-	"github.com/nektos/act/pkg/artifactcache"
-	"github.com/nektos/act/pkg/artifacts"
-	"github.com/nektos/act/pkg/common"
-	"github.com/nektos/act/pkg/container"
-	"github.com/nektos/act/pkg/model"
-	"github.com/nektos/act/pkg/runner"
 )
 
 // Execute is the entry point to running the CLI
@@ -147,7 +149,7 @@ func bugReport(ctx context.Context, version string) error {
 	report := sprintf("act version:", version)
 	report += sprintf("GOOS:", runtime.GOOS)
 	report += sprintf("GOARCH:", runtime.GOARCH)
-	report += sprintf("NumCPU:", fmt.Sprint(runtime.NumCPU()))
+	report += sprintf("NumCPU:", strconv.Itoa(runtime.NumCPU()))
 
 	var dockerHost string
 	var exists bool
@@ -216,7 +218,7 @@ func bugReport(ctx context.Context, version string) error {
 	report += sprintf("\tOS version:", info.OSVersion)
 	report += sprintf("\tOS arch:", info.Architecture)
 	report += sprintf("\tOS kernel:", info.KernelVersion)
-	report += sprintf("\tOS CPU:", fmt.Sprint(info.NCPU))
+	report += sprintf("\tOS CPU:", strconv.Itoa(info.NCPU))
 	report += sprintf("\tOS memory:", fmt.Sprintf("%d MB", info.MemTotal/1024/1024))
 
 	report += fmt.Sprintln("\tSecurity options:")
@@ -305,9 +307,7 @@ func readEnvs(path string, envs map[string]string) bool {
 		if err != nil {
 			log.Fatalf("Error loading from %s: %v", path, err)
 		}
-		for k, v := range env {
-			envs[k] = v
-		}
+		maps.Copy(envs, env)
 		return true
 	}
 	return false
@@ -330,7 +330,7 @@ func parseMatrix(matrix []string) map[string]map[string]bool {
 	return matrixes
 }
 
-//nolint:gocyclo
+//nolint:gocyclo // function handles many cases
 func newRunCommand(ctx context.Context, input *Input) func(*cobra.Command, []string) error {
 	return func(cmd *cobra.Command, args []string) error {
 		if input.jsonLogger {
@@ -511,7 +511,7 @@ func newRunCommand(ctx context.Context, input *Input) func(*cobra.Command, []str
 			log.Warnf(deprecationWarning, "privileged", "--privileged")
 		}
 		if len(input.usernsMode) > 0 {
-			log.Warnf(deprecationWarning, "userns", fmt.Sprintf("--userns=%s", input.usernsMode))
+			log.Warnf(deprecationWarning, "userns", "--userns="+input.usernsMode)
 		}
 		if len(input.containerCapAdd) > 0 {
 			log.Warnf(deprecationWarning, "container-cap-add", fmt.Sprintf("--cap-add=%s", input.containerCapAdd))