Do incremental SVN checkouts

In hydra-evaluator, reuse an SVN working copy between runs (similar to
what we do with Git and other input types).  This reduces network
traffic in the common case.

Also, don't use nix-prefetch-svn.  It doesn't do anything useful.

src/script/Makefile.am

@@ -1,9 +1,5 @@
 EXTRA_DIST = \
   hydra-control \
-  nix-prefetch-svn \
-  nix-prefetch-git \
-  nix-prefetch-bzr \
-  nix-prefetch-hg \
   $(bin_SCRIPTS)
 
 bin_SCRIPTS = \
@@ -13,7 +9,6 @@ bin_SCRIPTS = \
   hydra-server \
   hydra-update-gc-roots \
   hydra-create \
-  nix-prefetch-svn \
   nix-prefetch-git \
   nix-prefetch-bzr \
   nix-prefetch-hg

src/script/nix-prefetch-svn

@@ -1,79 +0,0 @@
-#! /bin/sh -e
-
-url=$1
-rev=$2
-expHash=$3
-
-hashType=$NIX_HASH_ALGO
-if test -z "$hashType"; then
-    hashType=sha256
-fi
-if test -z "$hashFormat"; then
-    hashFormat=--base32
-fi
-
-if test -z "$url"; then
-    echo "syntax: nix-prefetch-svn URL [REVISION [EXPECTED-HASH]]" >&2
-    exit 1
-fi
-
-test -n "$rev" || rev="HEAD"
-
-repoName=$(echo $url | sed '
-  s,.*/\([^/]\+\)/trunk/*$,\1,;t
-  s,.*/\([^/]\+\)/branches/\([^/]\+\)/*$,\1-\2,;t
-  s,.*/\([^/]\+\)/tags/\([^/]\+\)/*$,\1-\2,;t
-  s,.*/\([^/]\+\)/*$,\1,;t
-')
-dstFile=$repoName-r$rev
-
-# If the hash was given, a file with that hash may already be in the
-# store.
-if test -n "$expHash"; then
-    finalPath=$(nix-store --print-fixed-path --recursive "$hashType" "$expHash" $dstFile)
-    if ! nix-store --check-validity "$finalPath" 2> /dev/null; then
-        finalPath=
-    fi
-    hash=$expHash
-fi
-
-
-# If we don't know the hash or a path with that hash doesn't exist,
-# download the file and add it to the store.
-if test -z "$finalPath"; then
-    tmpPath=/tmp/svn-checkout-tmp-$$
-    tmpFile=$tmpPath/$dstFile
-    mkdir $tmpPath
-
-    trap "rm -rf $tmpPath" EXIT
-
-    # Perform the checkout.
-    if test "$NIX_PREFETCH_SVN_LEAVE_DOT_SVN" != 1
-    then
-	command="export"
-    else
-	command="checkout"
-    fi
-
-    echo p | svn "$command" --quiet -r "$rev" "$url" "$tmpFile" >&2
-
-    # Compute the hash.
-    hash=$(nix-hash --type $hashType $hashFormat $tmpFile)
-    if ! test -n "$QUIET"; then echo "hash is $hash" >&2; fi
-
-    # Add the downloaded file to the Nix store.
-    finalPath=$(nix-store --add-fixed --recursive "$hashType" $tmpFile)
-
-    if test -n "$expHash" -a "$expHash" != "$hash"; then
-        echo "hash mismatch for URL \`$url'"
-        exit 1
-    fi
-fi
-
-if ! test -n "$QUIET"; then echo "path is $finalPath" >&2; fi
-
-echo $hash
-
-if test -n "$PRINT_PATH"; then
-    echo $finalPath
-fi