Update travis to create a "latest" symlink.

.travis.yml

@@ -16,6 +16,8 @@ after_success:
 - LD_LIBRARY_PATH=$WXDIR/lib package/linux/make_archive.sh linux-x64
 - package/linux/appimage.sh x86_64
 - package/deploy/sftp.sh linux ~/slic3r-upload.rsa *.bz2 Slic3r*.AppImage
+- package/deploy/sftp-symlink.sh linux ~/slic3r-upload.rsa AppImage Slic3r*.AppImage
+- package/deploy/sftp-symlink.sh linux ~/slic3r-upload.rsa bz2 *.bz2
 branches:
   only:
   - master

package/deploy/sftp-symlink.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+# Prerequisites
+# Environment Variables:
+#   UPLOAD_USER - user to upload to sftp server
+# KEY is assumed to be path to a ssh key for UPLOAD_USER
+
+DIR=$1
+shift
+KEY=$1
+shift
+EXT=$1
+shift
+FILES=$*
+
+source $(dirname $0)/../common/util.sh
+set_pr_id
+set_branch
+if [ ! -z ${PR_ID+x} ] || [ $current_branch != "master" ]; then
+    DIR=${DIR}/branches
+fi
+
+if [ -s $KEY ]; then
+    for i in $FILES; do 
+         filepath=$(readlink -f "$i")
+         tmpfile=$(mktemp)
+         echo "rm -f slic3r-${current_branch}-latest.${EXT}" > $tmpfile
+         echo "symlink slic3r-${current_branch}-latest.${EXT} $filepath" >> $tmpfile 
+         sftp -b $tmpfile -i$KEY "${UPLOAD_USER}@dl.slic3r.org:$DIR/"
+         result=$?
+         if [ $? -eq 1 ]; then 
+             echo "Error with SFTP symlink"
+             exit $result; 
+         fi
+    done
+else
+    echo "$KEY is not available, not symlinking." 
+fi
+exit $result