Make it super simple to use on Travis CI

[probonopd]

A common use case for linuxdeployqt is to use it on Travis CI after the make command.

Currently quite some hoops are necessary. We should make linuxdeployqt so intelligent as to be a one-line operation, ideally replacing most of the manual work of

language: cpp
compiler: gcc
sudo: require
dist: trusty

before_install:
    - sudo add-apt-repository ppa:beineri/opt-qt58-trusty -y
    - sudo apt-get update -qq
    
install: 
    - sudo apt-get -y install qt58base
    - source /opt/qt58/bin/qt58-env.sh

script:
  - qmake PREFIX=/usr
  - make -j4
  - sudo apt-get -y install checkinstall
  - sudo checkinstall --pkgname=app --pkgversion="1" --pkgrelease="1" --backup=no --fstrans=no --default --deldoc 
  - mkdir appdir ; cd appdir
  - dpkg -x ../app_1-1_amd64.deb . ; find .
  - cp ./usr/share/applications/*.desktop .
  - cp ./usr/share/icons/hicolor/48x48/apps/*.png .
  - cd .. 
  - wget -c "https://github.com/probonopd/linuxdeployqt/releases/download/3/linuxdeployqt-3-x86_64.AppImage" 
  - chmod a+x linuxdeployqt*.AppImage
  - unset QTDIR; unset QT_PLUGIN_PATH ; unset LD_LIBRARY_PATH
  - ./linuxdeployqt*.AppImage ./appdir/usr/bin/* -bundle-non-qt-libs -qmldir=$(readlink -f /opt/qt5*/qml/)
  - ./linuxdeployqt*.AppImage ./appdir/usr/bin/* -appimage -qmldir=$(readlink -f /opt/qt5*/qml/)
  - find ./appdir -executable -type f -exec ldd {} \; | grep " => /usr" | cut -d " " -f 2-3 | sort | uniq
  - curl --upload-file ./APPNAME*.AppImage https://transfer.sh/APPNAME-git.$(git rev-parse --short HEAD)-x86_64.AppImage 

We could, as part of linuxdeployqt and/or the underlying appimagetool,

• Unset the offending Qt environment variables that prevent linuxdeployqt from running
• Remove the need for -qmldir=$(readlink -f /opt/qt5*/qml/)
• Check if there is exactly one desktop file in usr/share/applications and if so, use that. Otherwise have the user specify the desktop file rather than the executable and figure out the executable and icon from there, hence doing the copying automatically
• Use checkinstall. This is because I could not figure out a reliable method of installing to a different location than /usr - seems not needed in most cases
• Optionally, use the git and/or travis information to determine the version
• Optionally, upload to transfer.sh

In the current continuous build, the following is implemented:

language: cpp
compiler: gcc
sudo: require
dist: trusty

before_install:
    - sudo add-apt-repository ppa:beineri/opt-qt58-trusty -y
    - sudo apt-get update -qq
    
install: 
    - sudo apt-get -y install qt58base
    - source /opt/qt58/bin/qt58-env.sh

script:
  - qmake PREFIX=/usr
  - make -j4
  - sudo make INSTALL_ROOT=appdir install ; sudo chown -R $USER appdir ; find appdir/

after_success:
  - wget -c "https://github.com/probonopd/linuxdeployqt/releases/download/continuous/linuxdeployqt-continuous-x86_64.AppImage" 
  - chmod a+x linuxdeployqt*.AppImage
  - unset QTDIR; unset QT_PLUGIN_PATH ; unset LD_LIBRARY_PATH
  - ./linuxdeployqt*.AppImage ./appdir/usr/share/applications/*.desktop -bundle-non-qt-libs
  - ./linuxdeployqt*.AppImage ./appdir/usr/share/applications/*.desktop -appimage
  - find ./appdir -executable -type f -exec ldd {} \; | grep " => /usr" | cut -d " " -f 2-3 | sort | uniq
  - curl --upload-file ./APPNAME*.AppImage https://transfer.sh/APPNAME-git.$(git rev-parse --short HEAD)-x86_64.AppImage

Note that if qmake does not allow for make install or does not install the desktop file and icon, then change it similar to https://github.com/probonopd/FeedTheMonkey/blob/master/FeedTheMonkey.pro.

[probonopd]

Similar build procedures used for

• https://github.com/dannagle/PacketSender | Generate AppImage from Travis CI build artefacts dannagle/PacketSender#66
• https://github.com/nuttyartist/notes | Generate AppImage on each git push nuttyartist/notes#119 (with desktopintegration - could also be automated)
• https://github.com/Swordfish90/cool-retro-term | Generate AppImage of each build on Travis CI Swordfish90/cool-retro-term#336
• https://github.com/leozide/leocad/ | Generate and upload an AppImage on each Travis CI run leozide/leocad#22
• https://github.com/Teuniz/DSRemote | https://github.com/Teuniz/DSRemote/pull/14
• https://github.com/Teuniz/EDFbrowser/ | https://github.com/Teuniz/EDFbrowser/pull/31
• https://github.com/trevorsandy/lpub3d/ | https://github.com/probonopd/lpub3d/blob/patch-1/.travis.yml
• https://github.com/KDAB/GammaRay/ | Add Travis CI builds KDAB/GammaRay#325 (has executables outside of usr/bin which needs some additional trickery)
• https://github.com/LongSoft/UEFITool/ | Compile on Travis CI LongSoft/UEFITool#71
• https://github.com/Rodmg/esptool-gui/ | Generate AppImage for Linux Rodmg/esptool-gui#2
• https://github.com/neuro-sys/tumblr-downloader-client/ | Fix AppImage generation neuro-sys/tumblr-likes-downloader#18
• https://github.com/psemiletov/eko/ | Continuous builds on Travis CI psemiletov/eko#4
• https://github.com/sqlitebrowser/sqlitebrowser/ | Create AppImage, closes #968 sqlitebrowser/sqlitebrowser#969
• https://github.com/socnetv/ | Generate AppImage of each Travis CI build socnetv/app#20
• https://github.com/dridk/cuterest/ | Generate AppImage dridk/cuterest#34
• https://github.com/labsquare/fastQt/ | Generate AppImage on Travis CI labsquare/FastQt#50
• https://github.com/jeena/FeedTheMonkey | https://github.com/jeena/FeedTheMonkey/pull/14/files (with qml)
• https://github.com/JvanKatwijk/qt-dab | Continuous builds for Linux on Travis CI JvanKatwijk/qt-dab#33 (with older Qt)
• https://github.com/hteso/iaito/ | Compile on Travis CI and upload AppImage for each build hteso/iaito#54

Attention: These might all suffer from #80 - to be fixed.

Once this is closed, should see if we can simplify their .travis.yml files.