Fix fileformat for newly created files

Fixes #1575

internal/buffer/buffer.go

@@ -297,7 +297,21 @@ func NewBuffer(r io.Reader, size int64, path string, startcursor Loc, btype BufT
 
 		if !hasBackup {
 			reader := bufio.NewReader(transform.NewReader(r, enc.NewDecoder()))
-			b.LineArray = NewLineArray(uint64(size), FFAuto, reader)
+
+			var ff FileFormat = FFAuto
+
+			if size == 0 {
+				// for empty files, use the fileformat setting instead of
+				// autodetection
+				switch b.Settings["fileformat"] {
+				case "unix":
+					ff = FFUnix
+				case "dos":
+					ff = FFDos
+				}
+			}
+
+			b.LineArray = NewLineArray(uint64(size), ff, reader)
 		}
 		b.EventHandler = NewEventHandler(b.SharedBuffer, b.cursors)
 

internal/buffer/line_array.go

@@ -87,6 +87,8 @@ func NewLineArray(size uint64, endings FileFormat, reader io.Reader) *LineArray
 	br := bufio.NewReader(reader)
 	var loaded int
 
+	la.Endings = endings
+
 	n := 0
 	for {
 		data, err := br.ReadBytes('\n')

runtime/help/options.md

@@ -117,12 +117,15 @@ Here are the available options:
 	default value: `false`
 
 * `fileformat`: this determines what kind of line endings micro will use for
-   the file. UNIX line endings are just `\n` (linefeed) whereas dos line
+   the file. Unix line endings are just `\n` (linefeed) whereas dos line
    endings are `\r\n` (carriage return + linefeed). The two possible values for
    this option are `unix` and `dos`. The fileformat will be automatically
    detected (when you open an existing file) and displayed on the statusline,
    but this option is useful if you would like to change the line endings or if
-   you are starting a new file.
+   you are starting a new file. Changing this option while editing a file will
+   change its line endings. Opening a file with this option set will only have
+   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`