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There are two subpackages (irfs, celestialSources) which have subsubpackages (that is, separately taggable physical subdirectories). celestialSources belongs to both ST and GR.  SCons and Release Manager recognize subpackages and subsubpackages by the existence of a file called SConscript.  In addition to specifying to SCons how to build the package, this file also contains version information.

Handling subsubpackages

The single fact causing us the most grief may be this: CVS tags apply to a directory (optionally recursively); git supports tags only of entire repositories.  Hence we surely need separate repositories for subpackages.    It's less clear what to do about subsubpackages.  There are only two subpackages with subsubpackages: celestialSources and irfs.   Our custom subpackage-tagging software goes to extra trouble to avoid tagging subsubpackages when the parent subpackage is tagged.

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