* fetchgit and nix-prefetch-git

svn path=/nixpkgs/trunk/; revision=16035

pkgs/build-support/fetchgit/nix-prefetch-git

@@ -0,0 +1,66 @@
+#! /bin/sh -e
+
+url=$1
+rev=$2
+expHash=$3
+
+hashType=$NIX_HASH_ALGO
+if test -z "$hashType"; then
+    hashType=md5
+fi
+
+if test -z "$url"; then
+    echo "syntax: nix-prefetch-git URL [REVISION [EXPECTED-HASH]]" >&2
+    exit 1
+fi
+
+# 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" git-export)
+    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/git-checkout-tmp-$$
+    tmpFile=$tmpPath/git-export
+    mkdir $tmpPath
+
+    trap "rm -rf $tmpPath" EXIT
+
+    # Perform the checkout.
+    git clone "$url" $tmpFile
+    if test -n "$rev"; then
+      cd $tmpFile
+      echo $tmpFile
+      git checkout $rev
+    fi
+    find $tmpFile -name .git\* | xargs rm -rf
+
+    # Compute the hash.
+    hash=$(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