add backToParent macro

input/projects/3d-printing/bed-leveling-util.md

 update: 2016-06-12
 ---
 
-<span class="listdesc">[...back to 3D-Printing overview](3d-printing.html)</span>
+<!--% backToParent() %-->
 
 This is a manual Mesh Bed Leveling GUI utility for 3D printers with Marlin Firmware.
 

input/projects/3d-printing/ctc-i3.md

 comments: true
 ---
 
-<span class="listdesc">[...back to 3D-Printing overview](3d-printing.html)</span>
+<!--% backToParent() %-->
 
 The CTC i3 Pro B is a very cheap chinese Prusa i3 clone.
 I bought it a couple of years ago for about 110 Euros.

input/projects/3d-printing/fabrikator-mini.md

 comments: true
 ---
 
-<span class="listdesc">[...back to 3D-Printing overview](3d-printing.html)</span>
-
-**More content coming soon!**
+<!--% backToParent() %-->
 
 I bought the [Fabrikator Mini V1.5 from HobbyKing](https://hobbyking.com/en_us/fabrikator-mini-3d-printer-transparent-eu-230v-v1-5.html) in about March 2016.
 So that's pretty much exactly three and a half years ago, at the time of this writing.

input/projects/3d-printing/ikea-lack.md

 comments: true
 ---
 
-<span class="listdesc">[...back to 3D-Printing overview](3d-printing.html)</span>
+<!--% backToParent() %-->
 
 As is common in the 3D printing community, I have built myself a tower of Ikea Lack tables to store my printers in.
 It has three levels.

input/projects/3d-printing/octoprint.md

 comments: true
 ---
 
-<span class="listdesc">[...back to 3D-Printing overview](3d-printing.html)</span>
+<!--% backToParent() %-->
 
 All my 3D printers are connected to a Raspberry Pi running [OctoPrint](https://octoprint.org/).
 For ease of use, I suggest downloading and installing a pre-made [OctoPi image](https://octoprint.org/download/).

input/projects/3d-printing/octotray.md

 update: 2021-05-13
 ---
 
-<span class="listdesc">[...back to 3D-Printing overview](3d-printing.html)</span>
+<!--% backToParent() %-->
 
 To quickly print new stuff on one of my printers, I am using the [OctoPrint](https://octoprint.org) integration of [PrusaSlicer](https://github.com/prusa3d/PrusaSlicer).
 Unfortunately, it does not allow me to turn on the printers power supply using the Raspberry Pi.

input/projects/quadcopters/aurora100.md

 parent: quadcopters
 position: 20
 date: 2017-07-17
-update: 2021-05-21
 ---
 
-<span class="listdesc">[...back to RC-Vehicles overview](quadcopters.html)</span>
+<!--% backToParent() %-->
 
 Not being totally happy with the power available with [my 2S xyAurora90](aurora90.html) I decided to build a 3S Aurora100 in July 2017.
 

input/projects/quadcopters/aurora90.md

 parent: quadcopters
 position: 30
 date: 2017-03-07
-update: 2021-05-21
 ---
 
-<span class="listdesc">[...back to RC-Vehicles overview](quadcopters.html)</span>
+<!--% backToParent() %-->
 
 The build started at the end of January 2017 and it was my main copter for flights indoors and outside in the garden for a long time.
 

input/projects/quadcopters/lx5.md

 parent: quadcopters
 position: 10
 date: 2017-11-01
-update: 2021-05-21
 ---
 
-<span class="listdesc">[...back to RC-Vehicles overview](quadcopters.html)</span>
+<!--% backToParent() %-->
 
 At the end of 2017 I had to give in to the urge of building a bigger more powerful copter.
 After my first failed attempts with large copters, gaining some experience with smaller frames seemed useful.

macros.py

 BASE_URL = "https://www.xythobuz.de"
 
 # -----------------------------------------------------------------------------
+# sub page helper macro
+# -----------------------------------------------------------------------------
+
+def backToParent():
+    url = page.get("parent", "") + ".html"
+    posts = [p for p in pages if p.url == url]
+    if len(posts) > 0:
+        p = posts[0]
+        print '<span class="listdesc">[...back to ' + p.title + ' overview](' + p.url + ')</span>'
+
+# -----------------------------------------------------------------------------
 # table helper macro
 # -----------------------------------------------------------------------------