[Monotone-devel] Mark merge for existence

[William Uther]

Hi,

  I'm looking at how to get rid of die-die-die merge for files.  As  
noted by others, if we used mark-merge here then we'd be able to un- 
delete and re-delete, and everything would "just work".

  As a first step I'd like to make a version of monotone that  
remembers the new 'existence' marks when the file exists (i.e. add  
existence marks to the current code without trying to remember them  
when a file is deleted - no it wont change anything, but it is a  
necessary step).

  The problem is that there seem to be a couple of different places  
that marks and rosters are generated / merged and I want to make sure  
I understand what is going on before I play with things - this is  
fairly important code. :)

  Let's consider the call chain following the "merge" command [I've  
included only one branch in the call chain where  
interactive_merge_and_store() calls roster_merge() then  
store_roster_merge_result()]:

  cmd_merging.cc : CMD(merge)
  cmd_merging.cc : merge_two()
  merge.cc : interactive_merge_and_store()   # loads the left & right  
rosters and marks from db
  roster_merge.cc : roster_merge()         merge.cc :  
store_roster_merge_result()
                                           database.cc :  
database::put_revision()
                                           database.cc :  
put_roster_for_revision()
                                           roster.cc :  
make_roster_for_revision()
                                           roster.cc :  
make_roster_for_merge()
                                           roster.cc :  
mark_merge_roster()  # much happens here
                                           roster.cc :   
mark_unmerged_node()  and  mark_merged_node()

  It seems that roster_merge() does the main merge, but then  
mark_merge_roster() does a lot of very similar work to build up the  
new marking map just before it is actually written to the db.  This  
seems a little convoluted.  Is there some reason for this I'm missing,  
or is it just... historical?

  That means that if I want to add new existence marks, I'd need to  
add them both in roster_merge() and in mark_merge_roster().  Are there  
any other places I should look at?

  Oh, and I've had to change things like roster.cc:push_marking().   
I'd prefer to update some database format ID so that I don't get my  
db's all confused while working on different versions of MTN.  Where  
would I find that in the code?

Cheers,

Will        :-}