git grep doesn't accept -- to separate branch from filename -

i have both file , branch called atlas, trips git when want search in using git grep:

$ git grep asdf atlas -- fatal: ambiguous argument 'atlas': both revision , filename use '--' separate paths revisions, this: 'git <command> [<revision>...] -- [<file>...]'  $ git grep asdf atlas -- . fatal: ambiguous argument 'atlas': both revision , filename use '--' separate paths revisions, this: 'git <command> [<revision>...] -- [<file>...]' 

with git log, can append -- fix it:

$ git log -1 --oneline atlas fatal: ambiguous argument 'atlas': both revision , filename use '--' separate paths revisions, this: 'git <command> [<revision>...] -- [<file>...]'  $ git log -1 --oneline atlas -- 690eca5 atlas: unit tests 

how achieve same result git grep?

edit: clarify: want search asdf in every file in branch called atlas.

try this:

git grep asdf atlas:

the colon used specifying refspec format <source>:<destination>, can leave destination empty , provide source, in case makes clear referring branch , not file.

you can learn more refspecs here.