patch 9.0.1653: Amiga: default 'viewdir' may not work

Problem:    Amiga: default 'viewdir' may not work.
Solution:   Use "home:" instead of "$VIM". Add a test. (Christian Brabandt,
            closes #12576)

runtime/doc/options.txt

@@ -8912,9 +8912,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 	displayed when 'verbosefile' is set.
 
 						*'viewdir'* *'vdir'*
-'viewdir' 'vdir'	string	(default for Amiga "$VIM/vimfiles/view",
+'viewdir' 'vdir'	string	(default for Amiga "home:vimfiles/view",
 					 for Win32: "$HOME/vimfiles/view",
-					 for Unix: "~/.vim/view",
+					 for Unix: "$HOME/.vim/view",
 					 for macOS: "$VIM/vimfiles/view"
 					 for VMS: "sys$login:vimfiles/view")
 			global

src/os_amiga.h

@@ -199,7 +199,7 @@ typedef long off_t;
 #endif
 
 #ifndef DFLT_VDIR
-# define DFLT_VDIR	"$VIM/vimfiles/view"	// default for 'viewdir'
+# define DFLT_VDIR	"home:vimfiles/view"	// default for 'viewdir'
 #endif
 
 #ifndef DFLT_MAXMEM

src/testdir/setup.vim

@@ -30,6 +30,10 @@ if 1
   " Avoid storing shell history.
   let $HISTFILE = ""
 
+  " Have current $HOME available as $ORIGHOME.  $HOME is used for option
+  " defaults before we get here, and test_mksession checks that.
+  let $ORIGHOME = $HOME
+
   " Make sure $HOME does not get read or written.
   " It must exist, gnome tries to create $HOME/.gnome2
   let $HOME = getcwd() . '/XfakeHOME'

src/testdir/test_mksession.vim

@@ -1262,4 +1262,17 @@ func Test_mkview_manual_fold()
   bw!
 endfunc
 
+" Test default 'viewdir' value
+func Test_mkview_default_home()
+  if has('win32')
+    call assert_match('^' .. $ORIGHOME .. '/vimfiles', &viewdir)
+  elseif has('unix')
+    call assert_match('^' .. $ORIGHOME .. '/.vim', &viewdir)
+  elseif has('amiga')
+    call assert_match('^home:vimfiles', &viewdir)
+  elseif has('mac')
+    call assert_match('^' .. $VIM .. '/vimfiles', &viewdir)
+  endif
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1653,
 /**/
     1652,
 /**/