test-editor-filename: fix portability of fake editor command

 - /bin/bash doesn't exist on FreeBSD
 - edit is executed by cmd.exe on Windows

tests/test-editor-filename.t

@@ -1,63 +1,61 b''
 Test temp file used with an editor has the expected suffix.
 
   $ hg init
 
 Create an editor that writes its arguments to stdout and set it to $HGEDITOR.
 
   $ cat > editor.sh << EOF
-  > #!/bin/bash
   > echo "\$@"
   > exit 1
   > EOF
-  $ chmod +x editor.sh
   $ hg add editor.sh
-  $ HGEDITOR=$TESTTMP/editor.sh
+  $ HGEDITOR="sh $TESTTMP/editor.sh"
   $ export HGEDITOR
 
 Verify that the path for a commit editor has the expected suffix.
 
   $ hg commit
   *.commit.hg.txt (glob)
-  abort: edit failed: editor.sh exited with status 1
+  abort: edit failed: sh exited with status 1
   [255]
 
 Verify that the path for a histedit editor has the expected suffix.
 
   $ cat >> $HGRCPATH <<EOF
   > [extensions]
   > rebase=
   > histedit=
   > EOF
   $ hg commit --message 'At least one commit for histedit.'
   $ hg histedit
   *.histedit.hg.txt (glob)
-  abort: edit failed: editor.sh exited with status 1
+  abort: edit failed: sh exited with status 1
   [255]
 
 Verify that when performing an action that has the side-effect of creating an
 editor for a diff, the file ends in .diff.
 
   $ echo 1 > one
   $ echo 2 > two
   $ hg add
   adding one
   adding two
   $ hg commit --interactive --config ui.interactive=true --config ui.interface=text << EOF
   > y
   > e
   > q
   > EOF
   diff --git a/one b/one
   new file mode 100644
   examine changes to 'one'? [Ynesfdaq?] y
   
   @@ -0,0 +1,1 @@
   +1
   record change 1/2 to 'one'? [Ynesfdaq?] e
   
   *.diff (glob)
   editor exited with exit code 1
   record change 1/2 to 'one'? [Ynesfdaq?] q
   
   abort: user quit
   [255]