git-extra: force the Notepad helper to use UTF-8

When Notepad is set as commit message editor, this fix adds a UTF-8 BOM
to the file before Notepad opens the file.  This way Notepad is forced
to read and save the file as UTF-8, allowing commit messages with
international characters.

Previosly Notepad opened and saved the file in some ANSI codepage,
while Git was reading the file as UTF-8 creating problems when
international charaters were written.

The fix takes into account rares cases when we manually use other
encoding than UTF-8 for commit messegas via the git config
i18n.commitencoding variable.

Now Notepad is completely usable as commit message editor without using
external tools like Gitpad.

Note: as previously, this special handling only applies if the `notepad`
script is called with a path indicating a file residing inside the
`.git/` directory.

[jes: adjusted code style, fixed checksums, clarified that this really
only affects Git files]

This fixes https://github.com/git-for-windows/git/issues/818 and closes
https://github.com/git-for-windows/build-extra/pull/123.

Signed-off-by: Dimitrij Mijoski <dmjpp@hotmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

git-extra/PKGBUILD

@@ -37,7 +37,7 @@ source=('inputrc'
 md5sums=('3fab57079f0322efe256e95fe29d516f'
          'e7ad03fffc29e619e402dbd5ec9ef74c'
          'bfb591886b2a28af3334521e71198b74'
-         '6ad699cbc3c4693fa75fb5d5d25d0e26'
+         '11d0e9aad647db83c56d9a89608baf11'
          'e3b411a4f2e6553e41d0c4261160dd7d'
          'fb92ea53ef01b4f60ed04eabac81e2c7'
          '7180794bfa88c1f687c1a7940fc62293'

git-extra/notepad

@@ -15,7 +15,10 @@ die "Usage: $0 <file>"
 
 if test -f "$1"
 then
-	unix2dos.exe "$1"
+	case "$(git config i18n.commitencoding 2>/dev/null)" in
+		''|utf-8|utf8) unix2dos.exe -m "$1";;
+		*) unix2dos.exe "$1";;
+	esac
 fi &&
 notepad.exe "$1" &&
 dos2unix.exe "$1" &&