Ticket for the trouble described at [http://www.mail-archive.com/fossil-users@lists.fossil-scm.org/msg05786.html]

Error:
<verbatim>
.... [many updates]
RENAME a.cmd -> a2.cmd
fossil: SQLITE_CONSTRAINT: abort at 34 in [UPDATE vfile SET                                        
pathname='a2.cmd', origname=coalesce(origname,pathname) WHERE                                      
id=1793175 AND vid=14998]: columns pathname, vid are not unique                                    
fossil: columns pathname, vid are not unique                                                       
.... [many undo]                                                                                   
fossil: SQLITE_BUSY: statement aborts at 2: [ROLLBACK] cannot rollback                             
transaction - SQL statements in progress                                                           
</verbatim>

Running with "merge --debug trunk":
<verbatim>
P->M at 15956> c0224914b6: 4198[a2.cmd] -> 0[]                                                     
P->M at 15957> 9d69a325f1: 2405[a.cmd] -> 0[]                                                      
P->M at 15957> 9d69a325f1: 2405[a.cmd] ->                                                          
4198[a2.cmd]                                                                                       
P->M summary 2405[a.cmd] -> 4198[a2.cmd]                                                           
186: ridv=151  ridp=151  ridm=15973 chnged=0 isexe=0                                               
    fn  = [a2.cmd]                                                                                 
    fnp = [a2.cmd]                                                                                 
    fnm = [a2.cmd]                                                                                 
187: ridv=14576 ridp=14576 ridm=15973 chnged=0 isexe=0                                             
    fn  = [a.cmd]                                                                                  
    fnp = [a.cmd]                                                                                  
    fnm = [a2.cmd]                                                                                 
</verbatim>