Allow wstool foreach commands to access state

[jayvdb]

foreach commands should be able to access the internal wstool variables, such as the root directory of the workspace , and the items being iterated over : the scmtype, local-name and uri.

Currently a wstool foreach command needs to do wstool info . --only scmtype,localname,uri to get this information, and separately wstool info --root if it doesnt want to derive the root from the localname.

This should be done using substitution variables in the command line, so that non-ros-aware commands can be used with wstool; .e.g

wstool foreach --git git clone -o upstream "{uri}" "{localname}"

(That solves #59 ;-)

A simpler solution is to stuff this information into ROS_* environment variables, so that ros-aware tools can easily obtain these values without invoking wstool info

[tkruse]

Not sure how this would solve #59, but in general the idea sounds ok. Not sure if many people would use this though, so if you don't do the pr, nobody might

[dirk-thomas]

Closing since the repository is about to be archived: see #154.