determining if a revision has a certain feature

[Neal Becker]

I'm fixing a program which collects results of my earlier program runs and 
plots them.  The plotter needs to know if the earlier run has a certain 
feature, which unfortunately I did not record in the logs.  But I did record 
the hg ID of the program run.

So how can I tell if the hg ID that was run contains the feature?  I know 
what changeset introduced it, so I could query whether an hg ID has that 
changeset.  I believe this can be done with hg log?