git-sed: pass the -r option to the xargs command
git-sed: pass the -r option to the xargs command

Prevents running sed when the search pattern does not match any files.

This results in sed printing an unnessecary warning:

$ git sed foo bar
sed: no input files

GuillaumeSeren/git-extras,hickey/git-extras,spacewander/git-extras,tj/git-extras