Add header for conda activate script

Author: j-woz

dev/conda/activate.sh

@@ -1,5 +1,18 @@
 #!/bin/sh
 
+# ACTIVATE SH
+
+# This is called when the user activates the Anaconda environment
+#      containing swift-t or swift-t-r .
+# If R_LIBS_USER is unset,
+#      R will add a default library location to .libPaths()
+# This commonly breaks R because the Anaconda R does not match other
+#      R installations on the same system.
+# Here, we force R_LIBS_USER to the Anaconda R library location.
+# This may make it more difficult for users to reuse libraries on the
+#      same system, but that is a small price to pay against very
+#      confusing error messages due to compiler incompatibilies.
+
 if [[ ! -z ${R_LIBS_USER+x} ]]; then
   export R_LIBS_USER_BACKUP="$R_LIBS_USER"
 fi