So, today I wanted to extract a copy of our ardrone 2.0 package from our repository as a separate hg repository, with all its history imported. A little bit of searching helped me get to the solution
a. Enable the convert extension for mercurial by adding the following lines to ~/.hgrc

b. Create a map file which would instruct hg on how to extract the subfolder
include cpp/bird_ros_pkgs/ardrone2
rename cpp/bird_ros_pkgs/ardrone2 .

the first line specifies the relative path of the folder I want to extract from the path of the repo. The next line redirects the contents of that folder to the root of the new repo (. refers to the root of the new repo)
c. Run the hg convert utility!
hg convert --filemap ~/map.txt ~/bird_repo ~/ardrone2_repo/

And that’s it!

Also, miscellaneous notes from October

1. Do not try to use colorgcc with ROS on ubuntu. It is a living nightmare. The issue lies in trying to symlink gcc and g++ to colorgcc and prepending the path to the symlinks to the PATH environment variable. However, many packages don’t really structure themselves well, and don’t seem to traverse through the PATH well. So, although for normal code colorgcc was working, it failed miserably for instance for my ardrone2 package, which uses custom (horrid cascading) makefiles.

2. The thesis theme for wordpress is pretty neat. Using the PHP hooks allows you a great amount of flexibility. Also, whenever using thesis, add the thesis_hooks plugin. It serves as a handy guide to view all the customisable hooks for versions before 2.0.

3. When working with tf, always waitForTransform()s before starting execution based on the transforms. Not doing so results in annoying exceptions. Also, rospy automatically spawns off threads for Subscribe and Publish. Keep that in mind, and use locks whenever necessary. Pickling does not work for objects with locks in them, so design classes that serve purely as data storage and pickle them through accessor classes that lock access to the instance.

4. In Simulink never run differentiation directly on a sensor input. Ideally, use a low pass filter, but for a quick estimation use a transfer function using the laplacian s/(1+2*pi*f*s). Also, try and replace algebraic loops involving differentiation with integration.

5. In Latex, to include multiple figures on the same line with their own captions (just like in my brand new SoP :D) use the subcaption package. Then include images like so
\subcaptionbox*{\footnotesize{}}{\includegraphics[width = 0.30\linewidth, trim=[left] [top] [right] [bottom], clip]{[path_to_image]}}~
\subcaptionbox*{\footnotesize{}}{\includegraphics[width = 0.30\linewidth, trim=[left] [top] [right] [bottom], clip]{[path_to_image]}}~

The ~ at the end specifies single unit space that Latex is not allowed to break a line at. I used 0.3 times the linewidth since I had three pictures in there.