tests/template: Make fake tarball with BusyBox

After thinking about it, I realized the `tar: lseek: Invalid seek` error
produced by the BusyBox `tar` on Alpine Linux might be eliminated by
having `tar` read from standard input rather than using `-f` to access
directly the `/dev/fd` file created by the process substitution.

Also updated all the `tar` commands to make their invocations more
consistent with one another.

Author: mbland

go-template

@@ -84,7 +84,7 @@ download_go_script_bash_tarball() {
   fi
   printf "Downloading framework from '%s'...\n" "$url"
 
-  if ! tar -xzf <("${download_cmd[@]}") || [[ ! -f "$unpacked_core" ]]; then
+  if ! tar -xzf - < <("${download_cmd[@]}") || [[ ! -f "$unpacked_core" ]]; then
     printf "Failed to download from '%s'.\n" "$url" >&2
     return 1
   elif [[ ! -d "$core_dir_parent" ]] && ! mkdir -p "$core_dir_parent" ; then

tests/template.bats

@@ -123,11 +123,11 @@ create_fake_tarball_if_not_using_real_url() {
   elif ! mkdir -p "$full_dir"; then
     printf 'Failed to create fake content dir %s\n' "$full_dir" >&2
     result='1'
-  elif ! tar xf <(tar cf - go-core.bash lib libexec) -C "$full_dir"; then
+  elif ! tar -xf - -C "$full_dir" < <(tar -cf - go-core.bash lib libexec); then
     printf 'Failed to mirror %s to fake tarball dir %s\n' \
       "$_GO_ROOTDIR" "$full_dir" >&2
     result='1'
-  elif ! tar cfz "$tarball" -C "$TEST_GO_ROOTDIR" "$dirname"; then
+  elif ! tar -czf "$tarball" -C "$TEST_GO_ROOTDIR" "$dirname"; then
     printf 'Failed to create fake tarball %s\n  from dir %s\n' \
       "$tarball" "$full_dir" >&2
     result='1'