is it possible to edit the commit message after the commit ?

[Zorba]

I'm presuming that because of the SHA1 hash this is impossible, but just 
maybe....?

I think in git one could rewrite history, but it was only for ppl who knew 
what they were doing, as it changed the hash and therefore the IDs of object 
(presumably the whole way down the linked list of chained versions).

I've made some commits and would like to go back and put some more detailed 
info into the commits describing the changes.

I know I could use tags but I'd prefer not to, as they're not as closely 
tied to the object as in git (seem to lag a version "behind" if you know 
what i mean).

I've looked through all the commands in man page and none seem appropriate 
so I'm guessing the answer is NO, but posting here in case I've missed 
something.

many thanks