hack: use Git-free ROOTDIR convention

Signed-off-by: Bjorn Neergaard <bjorn.neergaard@docker.com>

hack/generate-authors.sh

@@ -3,7 +3,7 @@
 set -e
 
 SCRIPTDIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-ROOTDIR="$(git -C "$SCRIPTDIR" rev-parse --show-toplevel)"
+ROOTDIR="$(cd "${SCRIPTDIR}/.." && pwd)"
 
 set -x
 

hack/validate/no-module

@@ -3,7 +3,7 @@
 # Check that no one is trying to commit a go.mod.
 
 SCRIPTDIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-ROOTDIR="$(git -C "$SCRIPTDIR" rev-parse --show-toplevel)"
+ROOTDIR="$(cd "${SCRIPTDIR}/../.." && pwd)"
 
 if test -e "${ROOTDIR}/go.mod"; then
 	{

hack/with-go-mod.sh

@@ -9,7 +9,7 @@
 set -e
 
 SCRIPTDIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-ROOTDIR="$(git -C "$SCRIPTDIR" rev-parse --show-toplevel)"
+ROOTDIR="$(cd "${SCRIPTDIR}/.." && pwd)"
 
 if test -e "${ROOTDIR}/go.mod"; then
 	{