nix-prefetch-darcs: print status to stderr; fetchdarcs: --no-cache in sandbox (#501607)

pkgs/build-support/fetchdarcs/builder.sh

@@ -20,7 +20,7 @@ set -o noglob
 success=
 for repository in $repositories; do
     echo "Trying to clone $repository $tagtext into $out …"
-    if darcs clone --lazy $tagflags "$repository" "$out"; then
+    if darcs clone --lazy --no-cache $tagflags "$repository" "$out"; then
         # remove metadata, because it can change
         rm -rf "$out/_darcs"
         success=1

pkgs/build-support/fetchdarcs/nix-prefetch-darcs

@@ -27,7 +27,7 @@ usage() {
 while [ $# -gt 0 ]; do
 	case "$1" in
 		--quiet)
-		  quiet=1; shift 1 ;;
+			quiet=1; shift 1 ;;
 		--name)
 			name="$2"; shift 2 ;;
 		--repo)
@@ -127,11 +127,7 @@ if [ -z "$final_path" ]; then
 
 	cd "$tmp_clone"
 	# Do not print Darcs progress to stdout (else stdout isn’t parsable JSON)
-	if [ -t 1 ]; then
-		darcs clone $clone_args "$repository" "$name" >/dev/tty
-	else
-		darcs clone $clone_args "$repository" "$name" >/dev/null
-	fi
+	darcs clone "$clone_args" "$repository" "$name" 1>&2
 	# Will put the current Darcs context into the store.
 	new_context="$tmp_clone/${name}-context.txt"
 	darcs log --repodir="$tmp_clone/$name" --context > "$new_context"