Make gofmt display *which* files it had a problem with

[dandv]

This failed build shows that

test -z $(gofmt -l $(find . -name '*.go'))

doesn't actually "list files whose formatting differs from gofmt's" as the help for -l claims.

find . -name '*.go' | xargs gofmt -l does display the offending files.

[sebastianbenz]

test ... will fail the build, which the other command won't... We need the best of both worlds.

[dandv]

badfiles=$(find . -name '*.go' | xargs gofmt -l); echo $badfiles; test -z $badfiles