Add --rev to update-source-version, add a generic unstable updater

pkgs/common-updater/scripts/update-source-version

@@ -10,7 +10,7 @@ die() {
 
 usage() {
     echo "Usage: $scriptName <attr> <version> [<new-source-hash>] [<new-source-url>]"
-    echo "                              [--version-key=<version-key>] [--system=<system>] [--file=<file-to-update>]"
+    echo "                              [--version-key=<version-key>] [--system=<system>] [--file=<file-to-update>] [--rev=<revision>]"
     echo "                              [--ignore-same-hash] [--print-changes]"
 }
 
@@ -30,6 +30,9 @@ for arg in "$@"; do
                 die "Could not find provided file $nixFile"
             fi
         ;;
+        --rev=*)
+            newRevision="${arg#*=}"
+        ;;
         --ignore-same-hash)
             ignoreSameHash="true"
         ;;
@@ -111,6 +114,13 @@ if [[ "$oldVersion" = "$newVersion" ]]; then
     exit 0
 fi
 
+if [[ -n "$newRevision" ]]; then
+    oldRevision=$(nix-instantiate $systemArg --eval -E "with import ./. {}; $attr.src.rev" | tr -d '"')
+    if [[ -z "$oldRevision" ]]; then
+        die "Couldn't evaluate source revision from '$attr.src'!"
+    fi
+fi
+
 # Escape regex metacharacter that are allowed in store path names
 oldVersionEscaped=$(echo "$oldVersion" | sed -re 's|[.+]|\\&|g')
 oldUrlEscaped=$(echo "$oldUrl" | sed -re 's|[${}.+]|\\&|g')
@@ -174,6 +184,15 @@ if cmp -s "$nixFile" "$nixFile.bak"; then
     die "Failed to replace source hash of '$attr' to a temporary hash!"
 fi
 
+# Replace new revision, if given
+if [[ -n "$newRevision" ]]; then
+    sed -i "$nixFile" -re "s|\"$oldRevision\"|\"$newRevision\"|"
+
+    if cmp -s "$nixFile" "$nixFile.bak"; then
+        die "Failed to replace source revision '$oldRevision' to '$newRevision' in '$attr'!"
+    fi
+fi
+
 # If new hash not given on the command line, recalculate it ourselves.
 if [[ -z "$newHash" ]]; then
     nix-build $systemArg --no-out-link -A "$attr.src" 2>"$attr.fetchlog" >/dev/null || true

pkgs/common-updater/unstable-updater.nix

@@ -0,0 +1,44 @@
+{ stdenv
+, writeShellScript
+, coreutils
+, git
+, nix
+, common-updater-scripts
+}:
+
+# This is an updater for unstable packages that should always use the latest
+# commit.
+{ url ? null # The git url, if empty it will be set to src.url
+}:
+
+let
+  updateScript = writeShellScript "unstable-update-script.sh" ''
+    set -ex
+
+    url="$1"
+
+    # By default we set url to src.url
+    if [[ -z "$url" ]]; then
+        url="$(${nix}/bin/nix-instantiate $systemArg --eval -E \
+                   "with import ./. {}; $UPDATE_NIX_ATTR_PATH.src.url" \
+            | tr -d '"')"
+    fi
+
+    # Get info about HEAD from a shallow git clone
+    tmpdir="$(${coreutils}/bin/mktemp -d)"
+    ${git}/bin/git clone --bare --depth=1 "$url" "$tmpdir"
+    pushd "$tmpdir"
+    commit_date="$(${git}/bin/git show -s --pretty='format:%cs')"
+    commit_sha="$(${git}/bin/git show -s --pretty='format:%H')"
+    popd
+    ${coreutils}/bin/rm -rf "$tmpdir"
+
+    # update the nix expression
+    ${common-updater-scripts}/bin/update-source-version \
+        "$UPDATE_NIX_ATTR_PATH" \
+        "unstable-$commit_date" \
+        --rev="$commit_sha"
+  '';
+
+in [ updateScript url ]
+

pkgs/development/compilers/qbe/default.nix

@@ -1,6 +1,9 @@
-{ stdenv, fetchgit }:
+{ stdenv
+, fetchgit
+, unstableGitUpdater
+}:
 
-stdenv.mkDerivation {
+stdenv.mkDerivation rec {
   pname = "qbe";
   version = "unstable-2019-07-11";
 
@@ -11,6 +14,9 @@ stdenv.mkDerivation {
   };
 
   makeFlags = [ "PREFIX=$(out)" ];
+
+  passthru.updateScript = unstableGitUpdater { };
+
   meta = with stdenv.lib; {
     homepage = "https://c9x.me/compile/";
     description = "A small compiler backend written in C";

pkgs/top-level/all-packages.nix

@@ -94,6 +94,8 @@ in
 
   genericUpdater = callPackage ../common-updater/generic-updater.nix { };
 
+  unstableGitUpdater = callPackage ../common-updater/unstable-updater.nix { };
+
   nix-update-script = callPackage ../common-updater/nix-update.nix { };
 
   ### Push NixOS tests inside the fixed point