nix-prefetch-darcs: use --repodir & remove now-unneeded cd

Author: toastal

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

@@ -132,18 +132,16 @@ if [ -z "$final_path" ]; then
 	else
 		darcs clone $clone_args "$repository" "$name" >/dev/null
 	fi
-	cd "$tmp_clone/$name"
 	# Will put the current Darcs context into the store.
 	new_context="$tmp_clone/${name}-context.txt"
-	darcs log --context > "$new_context"
+	darcs log --repodir="$tmp_clone/$name" --context > "$new_context"
 	final_context="$(nix-store --add-fixed "$hash_algo" "$new_context")"
 	# Darcs has a weak hash using the XOR of the patch hashes which is useful
 	# for other scripts
 	# https://darcs.net/Internals/Hashes
-	weak_hash="$(darcs show repo | awk '/^[[:space:]]*Weak Hash:/ { sub(/^[[:space:]]*Weak Hash:[[:space:]]*/, "", $0); printf $0 }')"
+	weak_hash="$(darcs show repo --repodir="$tmp_clone/$name" | awk '/^[[:space:]]*Weak Hash:/ { sub(/^[[:space:]]*Weak Hash:[[:space:]]*/, "", $0); printf $0 }')"
 	date="$(darcs log --repodir="$tmp_clone/$name" --max-count 1 | awk '/^Date:/ { sub(/^Date:[[:space:]]*/, "", $0); printf $0 }')"
 	date="$(date -u -d "$date" "+%Y-%m-%dT%H:%M:%SZ")"
-	cd - >/dev/null
 	rm -rf "$tmp_clone/$name/_darcs"
 
 	hash="$(nix-hash --type "$hash_algo" "$hash_format" "$tmp_clone/$name")"