DOC: Overview on local development

local_development.md

+# Setting up a local FSL development environment
+
+
+*This document is written under the assumption that you have FSL 6.1.0 or newer, installed via the fslinstaller script. These instructions will not work for manually managed FSL installations.*
+
+
+This document describes how to set up a local development environment for compiling FSL C/C++ projects. It  does **not** describe how to build conda packages for FSL projects - this is described in [building_fsl_conda_packages.md](building_fsl_conda_packages.md).
+
+
+A standard FSL installation comes with the `Makefile` machinery required to compile FSL C/C++ projects. All that you need to add is a C/C++ compiler. You can use your operating system compiler if you wish, but be warned that doing so will potentially compile your code in a different way to how the official FSL conda packages have been compiled.
+
+
+A better option is to use the [conda-forge](https://conda-forge.org/) compiler toolchain. You can install the conda-forge compilers directly into `$FSLDIR` like so:
+
+
+```
+# Set up your environment for FSL development. The
+# fsl-devel.sh script activates the $FSLDIR conda
+# environment, effectively adding $FSLDIR/bin to
+# your $PATH.
+source $FSLDIR/etc/fslconf/fsl-devel.sh
+
+# Install the conda-forge C/C++ compiler toolchain
+conda install -c conda-forge c-compiler cxx-compiler 
+```
+
+Now, when you want to work on a FSL project, you can follow these steps:
+
+```
+# Configure your environment for FSL development
+source $FSLDIR/etc/fslconf/fsl-devel.sh
+
+# Get a copy of the source 
+git clone https://git.fmrib.ox.ac.uk/fsl/randomise.git
+cd randomise 
+
+# Or work with the version you have installed
+cd $FSLDIR/src/randomise/
+
+# compile
+make
+
+# Re-install into your existing $FSLDIR
+make install
+
+# Or install into a different prefix
+export FSLDEVDIR=/my/local/dev/prefix
+make install
+```