This is my directory of hacks on Jam.

compile_with_SUB_rule.c
    A version of compile.c with a SUB rule (akin to sed's s//).
    Lightly tested.  Here in case I'll ever need it.
    
hdrscan_cache/...
    Modifications to Craig McPheeters' header scan code.  He has
    incorporated the changes (or, at least, the spirit of them) and I
    now use his version again.
    
hdrscan_on_target_fix/...
nt_msvcdir_fix/...
    Bug fixes.  See the change descriptions in each directory.

jamshell/...
    A stpuid shell for Win32.

patched_version/...    
    A custom patched version of Jam with all of the above changes and
    more.  See patched_version/LOCAL_CHANGES.txt.