Make default fileformat value suited to the OS (#3141)

Set fileformat by default to `dos` on Windows.

internal/config/settings.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"runtime"
 	"strconv"
 	"strings"
 
@@ -284,7 +285,7 @@ var defaultCommonSettings = map[string]interface{}{
 	"encoding":       "utf-8",
 	"eofnewline":     true,
 	"fastdirty":      false,
-	"fileformat":     "unix",
+	"fileformat":     defaultFileFormat(),
 	"filetype":       "unknown",
 	"hlsearch":       false,
 	"incsearch":      true,
@@ -319,6 +320,13 @@ var defaultCommonSettings = map[string]interface{}{
 	"wordwrap":       false,
 }
 
+func defaultFileFormat() string {
+	if runtime.GOOS == "windows" {
+		return "dos"
+	}
+	return "unix"
+}
+
 func GetInfoBarOffset() int {
 	offset := 0
 	if GetGlobalOption("infobar").(bool) {

runtime/help/options.md

@@ -157,7 +157,7 @@ Here are the available options:
    an effect if the file is empty/newly created, because otherwise the fileformat
    will be automatically detected from the existing line endings.
 
-	default value: `unix`
+	default value: `unix` on Unix systems, `dos` on Windows
 
 * `filetype`: sets the filetype for the current buffer. Set this option to
   `off` to completely disable filetype detection.