Move OS-related modules into a sub-package. NFC

Historically git-pages did not use those, but the codebase is growing
a bit out of hand and it seems like a good place to start.

src/backend_fs.go

@@ -12,6 +12,8 @@ import (
 	"path/filepath"
 	"strings"
 	"time"
+
+	sys "codeberg.org/git-pages/git-pages/src/sys"
 )
 
 type FSBackend struct {
@@ -66,8 +68,8 @@ func checkAtomicCAS(root *os.Root) bool {
 	root.Remove(fileName)
 	defer file.Close()
 
-	flockErr := FileLock(file)
-	funlockErr := FileUnlock(file)
+	flockErr := sys.FileLock(file)
+	funlockErr := sys.FileUnlock(file)
 	return (flockErr == nil && funlockErr == nil)
 }
 
@@ -295,7 +297,7 @@ func lockManifest(fs *os.Root, name string) (*manifestLockGuard, error) {
 	} else if err != nil {
 		return nil, fmt.Errorf("open: %w", err)
 	}
-	if err := FileLock(file); err != nil {
+	if err := sys.FileLock(file); err != nil {
 		file.Close()
 		return nil, fmt.Errorf("flock(LOCK_EX): %w", err)
 	}
@@ -304,7 +306,7 @@ func lockManifest(fs *os.Root, name string) (*manifestLockGuard, error) {
 
 func (guard *manifestLockGuard) Unlock() {
 	if guard.file != nil {
-		FileUnlock(guard.file)
+		sys.FileUnlock(guard.file)
 		guard.file.Close()
 	}
 }

src/main.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 	"time"
 
+	sys "codeberg.org/git-pages/git-pages/src/sys"
 	automemlimit "github.com/KimMachineGun/automemlimit/memlimit"
 	"github.com/c2h5oh/datasize"
 	"github.com/fatih/color"
@@ -720,7 +721,7 @@ func Main(versionInfo string) {
 		//
 		// Note that not all of the configuration is updated on reload. Listeners are kept as-is.
 		// The backend is not recreated (this is intentional as it allows preserving the cache).
-		OnReload(func() {
+		sys.OnReload(func() {
 			if newConfig, err := Configure(*configTomlPath, *secretTomlPath); err != nil {
 				logc.Println(ctx, "config: reload err:", err)
 			} else {
@@ -778,7 +779,7 @@ func Main(versionInfo string) {
 			logc.Println(ctx, "serve: ready")
 		}
 
-		WaitForInterrupt()
+		sys.WaitForInterrupt()
 		logc.Println(ctx, "serve: exiting")
 	}
 }

src/sys/flock_other.go

@@ -1,6 +1,6 @@
 //go:build !unix
 
-package git_pages
+package os
 
 import (
 	"fmt"

src/sys/flock_posix.go

@@ -1,6 +1,6 @@
 //go:build unix
 
-package git_pages
+package os
 
 import (
 	"os"

src/sys/signal.go

@@ -2,7 +2,7 @@
 // will do on Windows (tl;dr nothing calls the reload handler, the interrupt handler works
 // more or less how you'd expect).
 
-package git_pages
+package os
 
 import (
 	"os"