MAINT-1481: minor bug fix plus incomplete UI tweaks.

Test for existence of target name using -e rather than -f. (-d would work too,
but in this case we must respond to any name collision, whether file or
directory.)
Instead of terminating on failure, make sudo_mv return rc of the [sudo] mv
command to its caller. If the attempt to move new install to actual viewer
directory fails, restore previous viewer before failing.
When redirecting the script's stderr to updater.log, first save existing
stderr to another file descriptor, and restore it when we launch viewer.
Otherwise updater.log ends up collecting the viewer's duplicate stderr log
output!
The construct 'exec ... | program' doesn't work. In fact it causes any other
redirections on that command to fail too. Remove it -- real fix pending.

indra/viewer_components/updater/scripts/linux/update_install

@@ -53,7 +53,7 @@ function sudo_mv {
     # If we have write permission to both parent directories, shouldn't need
     # sudo.
     if [ -w "$(dirname "$1")" -a -w "$(dirname "$2")" ]
-    then mv "$1" "$2" || fail "Couldn't move $1 to $2"
+    then mv "$1" "$2"
     else # use one of the likely sudo programs
          sudo="$(which gksudo)"
          if [ -z "$sudo" ]
@@ -61,9 +61,9 @@ function sudo_mv {
          fi
          if [ -z "$sudo" ]
          then # couldn't find either one, just try it anyway
-              mv "$1" "$2" || fail "Couldn't move $1 to $2"
+              mv "$1" "$2"
          else # even with sudo, could fail, e.g. different filesystems
-              "$sudo" mv "$1" "$2" || fail "Couldn't move $1 to $2"
+              "$sudo" mv "$1" "$2"
          fi
     fi
 }
@@ -94,9 +94,9 @@ logname="$logsdir/updater.log"
 # move aside old updater.log; we're about to create a new one
 [ -f "$logname" ] && mv "$logname" "$logname.old"
 
-# Set up redirections for this script such that stderr is logged, while
-# special stdout messages drive our UI, as described in xmenity.
-exec 2> "$logname" | "$mydir/xmenity"
+# Set up redirections for this script such that stderr is logged. (But first
+# move the previous stderr to file descriptor 3.)
+exec 3>&2- 2> "$logname"
 # Piping to xmenity requires that we end with a line consisting of the string
 # "100" to terminate zenity progress bar.
 cleanup echo 100
@@ -131,19 +131,25 @@ INSTALL_DIR="$(cd "$mydir/.." ; pwd)"
 
 # Considering we're launched from a subdirectory of INSTALL_DIR, would be
 # surprising if it did NOT already exist...
-if [ -f "$INSTALL_DIR" ]
+if [ -e "$INSTALL_DIR" ]
 then backup="$INSTALL_DIR.backup"
      backupn=1
-     while [ -f "$backup" ]
+     while [ -e "$backup" ]
      do backup="$INSTALL_DIR.backup.$backupn"
         ((backupn += 1))
      done
-     sudo_mv "$INSTALL_DIR" "$backup"
+     sudo_mv "$INSTALL_DIR" "$backup" || fail "Couldn't move $INSTALL_DIR to $backup"
 fi
 # We unpacked the tarball into tempinstall. Move that.
-sudo_mv "$tempinstall" "$INSTALL_DIR"
+if ! sudo_mv "$tempinstall" "$INSTALL_DIR"
+then # If we failed to move the temp install to INSTALL_DIR, try to restore
+     # INSTALL_DIR from backup
+     sudo_mv "$backup" "$INSTALL_DIR"
+     fail "Couldn't move $1 to $2"
+fi
 
 rm -f "$tarball"
 
-# launch the updated viewer
-"$INSTALL_DIR/secondlife" &
+# Launch the updated viewer. Restore original stderr from file descriptor 3,
+# though -- otherwise updater.log gets cluttered with the viewer log!
+"$INSTALL_DIR/secondlife" 2>&3- &