* `fetchsvn' now requires the MD5 hash (as computed by `nix-hash') of

  the tree being fetched from a Subversion repository.  The revision
  number is now optional (and defaults to HEAD).

  This makes `fetchsvn' more pure.  First, a URL/revision tuple does
  not uniquely identify a file resource, since the repository itself
  might change.  Second, `svn:external' attributes can cause arbitrary
  resources to be exported.

  A script `nix-prefetch-svn' has been provided to determine the hash
  of a URL.

svn path=/nixpkgs/trunk/; revision=938

1 files changed, 47 insertions, 0 deletions

diff --git a/pkgs/build-support/fetchsvn/nix-prefetch-svn b/pkgs/build-support/fetchsvn/nix-prefetch-svn
new file mode 100755
index 000000000000..9d037032b1c7
--- /dev/null
+++ b/pkgs/build-support/fetchsvn/nix-prefetch-svn
@@ -0,0 +1,47 @@
+#! /bin/sh -e
+
+url=$1
+rev=$2
+
+if test -z "$url"; then
+    echo "syntax: nix-prefetch-svn URL [REVISION]" >&2
+    exit 1
+fi
+
+test -n "$rev" || rev="HEAD"
+
+# !!! hacky; we should have a way to query the location of the store.
+if storeDir=$(which nix-store); then
+    storeDir=$(dirname $(dirname "$storeDir"))/store
+else
+    storeDir=/nix/store
+fi
+
+# !!! race? should be relatively safe, `svn export' barfs if $tmpPath exists.
+tmpPath1=$storeDir/svn-checkout-tmp-$$
+
+# Perform the checkout.
+svn export -r "$rev" "$url" $tmpPath1 >&2
+
+# Compute the hash.
+hash=$(nix-hash $tmpPath1)
+echo "hash is $hash" >&2
+
+# Rename it so that the fetchsvn builder can find it.
+tmpPath2=$storeDir/svn-checkout-tmp-$hash
+test -e $tmpPath2 || mv $tmpPath1 $tmpPath2 # !!! race
+
+# Create a Nix expression that does a fetchsvn.
+nixExpr=$(dirname $(readlink -f $0))/../../system/i686-linux.nix
+storeExpr=$( \
+  echo "(import $nixExpr).fetchsvn {url=\"$url\"; rev=\"$rev\"; md5=\"$hash\";}" \
+  | nix-instantiate -)
+
+# Realise it.
+finalPath=$(nix-store -qnB --force-realise $storeExpr)
+
+echo "path is $finalPath" >&2
+
+rm -rf $tmpPath2 || true
+
+echo $hash