find and open conflict files from root git directory

[olshevskiy87]

fac could not open file with conflict if the user's current working directory differs from the git root directory. in this case fac writes something like "2018/01/28 22:12:43 open <...>: no such file or directory".

how to reproduce:

• say we have git repo /git/myrepo/ with subdir lib/ as a current working directory
• we also have file with conflict: /git/myrepo/main.go
• run fac
• the output will be "<...> open /git/myrepo/lib/main.go: no such file or directory"