I can't open files using just the filename from the current directory. Output below:
D:\Dropbox>fossil open test
SQLITE_ERROR: no such table: vvar
no such table: vvar
REPLACE INTO vvar(name,value)

If you have recently updated your fossil executable, you might
need to run "fossil all rebuild" to bring the repository
schemas up to date.

D:\Dropbox>fossil open .\test
SQLITE_ERROR: table vvar already exists
table vvar already exists

If you have recently updated your fossil executable, you might
need to run "fossil all rebuild" to bring the repository
schemas up to date.

D:\Dropbox>fossil open
SQLITE_ERROR: table vvar already exists
table vvar already exists

If you have recently updated your fossil executable, you might
need to run "fossil all rebuild" to bring the repository
schemas up to date.

D:\Dropbox>cd ..

D:\>fossil open Dropbox\test