Add AppImage build script (#739)

tools/appimage/make-appimage.sh

@@ -0,0 +1,80 @@
+#!/bin/bash
+
+set -e
+set -o pipefail
+
+show_usage_and_exit() {
+    echo "Usage: $0 <dir>"
+    echo "<dir> is the location of an extracted no-installer linux tarball of Natron"
+    exit 2
+}
+
+if [[ "$1" == "" ]]; then
+    show_usage_and_exit
+elif [[ ! -e "$1" ]]; then
+    echo "Error: $1 not found"
+    show_usage_and_exit
+elif [[ ! -d "$1" ]]; then
+    echo "Error: $1 is not a directory"
+    show_usage_and_exit
+fi
+
+# "convert" extracted dir to AppDir
+# this script is idempotent; existing files will be overwritten with the latest versions, subsequent runs will not change the outcome
+pushd "$1" &>/dev/null
+
+mkdir -p usr/share/{applications,icons/hicolor/256x256/apps,mime/packages}
+
+# copy icons for desktop entry and MIME package
+cp Resources/pixmaps/* usr/share/icons/hicolor/256x256/apps
+
+# create desktop entry
+cat > usr/share/applications/natron.desktop <<\EOF
+[Desktop Entry]
+Name=Natron
+Type=Application
+Exec=Natron
+Icon=natronIcon256_linux
+Categories=Video;
+EOF
+
+# create MIME package which the AppImage runtime can deploy
+# copied from bin/natron-mime.sh
+cat > usr/share/mime/packages/x-natron.xml <<\EOF
+<?xml version="1.0" encoding="UTF-8"?>
+<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
+    <mime-type type="application/x-natron">
+        <comment>Natron Project File</comment>
+        <icon name="natronProjectIcon_linux"/>
+        <glob-deleteall/>
+        <glob pattern="*.ntp"/>
+    </mime-type>
+</mime-info>
+EOF
+
+# copy files to AppDir root (would be done by tools like linuxdeploy, which we don't need for Natron)
+cp usr/share/applications/natron.desktop .
+cp usr/share/icons/hicolor/256x256/apps/natronIcon256_linux.png .
+
+# fetch and store version number for use in the AppImage name
+VERSION="$(bin/Natron --version | head -n1 | rev | awk '{print $1}' | rev || true)"
+export VERSION
+
+# create AppRun
+[[ ! -f AppRun ]] && ln -s Natron AppRun
+
+popd &>/dev/null
+
+# create AppImage
+
+# storing appimagetool in temporary directory
+tempdir="$(mktemp -d /tmp/natron-appimage-XXXXX)"
+_cleanup() { rm -rf "$tempdir"; }
+trap _cleanup EXIT
+
+pushd "$tempdir" &>/dev/null
+wget https://github.com/AppImage/AppImageKit/releases/download/continuous/appimagetool-x86_64.AppImage
+chmod +x appimagetool-x86_64.AppImage
+popd &>/dev/null
+
+"$tempdir"/appimagetool-x86_64.AppImage "$1"