diff --git a/build-aux/build-ports.sh b/build-aux/build-ports.sh
index 3782c355..38d92b02 100755
--- a/build-aux/build-ports.sh
+++ b/build-aux/build-ports.sh
@@ -242,6 +242,7 @@ download_archive_from_url() {(
        fi
      fi
      if ! echo "$SHA256SUM  $SORTIX_MIRROR_DIR/$PACKAGE/$ARCHIVE.untrusted" | sha256sum -c; then
+       sha256sum "$SORTIX_MIRROR_DIR/$PACKAGE/$ARCHIVE.untrusted"
        echo "warning: Wrong sha256sum after downloading $ARCHIVE from $URL" >&2
        exit 1
      fi
@@ -288,9 +289,11 @@ download_package() {(
 )}
 
 desired_version() {(
-  #unset ARCHIVE
-  #unset ARCHIVE_2
-  #. "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.info"
+  PACKAGE="$1"
+  unset DEVELOPMENT
+  unset ARCHIVE
+  unset ARCHIVE_2
+  . "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.info"
   VERSION_STAMP="$NAME"
   if [ -n "$ARCHIVE" ]; then
     VERSION_STAMP="$VERSION_STAMP.$VERSION.$SHA256SUM"
@@ -307,44 +310,105 @@ desired_version() {(
   if [ -f "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalize" ]; then
     VERSION_STAMP="$VERSION_STAMP.$(cat "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalize" | sha256sum | grep -Eo '^[^ ]*')"
   fi
+  if [ "$DEVELOPMENT" = true ]; then
+    VERSION_STAMP="$VERSION_STAMP.development"
+  fi
   echo "$VERSION_STAMP"
 )}
 
+diff_package() {(
+  # TODO: Only do this once the port is known to be cleaned.
+  cd "$SORTIX_PORTS_DIR/$1"
+  if [ -e "$1.normalized" ]; then
+    diff --no-dereference -Naur -- "$1.normalized" "$1" > "$1.patch" || true
+    if [ ! -s "$1.patch" ]; then rm "$1.patch"; fi
+    tix-execdiff -- "$1.normalized" "$1" > "$1.execpatch"
+    if [ ! -s "$1.execpatch" ]; then rm "$1.execpatch"; fi
+    # TODO: tix-rmpatch
+  fi
+)}
+
 extract_package() {(
   PACKAGE="$1"
-  VERSION_STAMP="$2"
+  unset DEVELOPMENT
   unset ARCHIVE
   unset ARCHIVE_2
   unset NEED_WRITABLE
   . "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.info"
-  VERSION_STAMP="$(desired_version)"
+  VERSION_STAMP="$(desired_version "$PACKAGE")"
+  OLD_VERSION_STAMP="$(cat "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version" || true)"
   if [ ! -e "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version" ] ||
      [ "$(cat "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version")" != "$VERSION_STAMP" ] ||
      [ ! -e "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version" ]; then
+    if [ -e "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version" ]; then
+      OLD_VERSION_STAMP="$(cat "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version")"
+      case "$OLD_VERSION_STAMP" in
+      *.development)
+        if [ "$DEVELOPMENT" = true ]; then
+          echo "error: $PACKAGE: Refusing to delete port in development"
+          echo "error: $PACKAGE: .version is currently: $OLD_VERSION_STAMP"
+          echo "error: $PACKAGE: .version should be: $VERSION_STAMP"
+          exit 1
+        fi
+        diff_package "$PACKAGE"
+      esac
+    fi
     echo "$VERSION_STAMP" > "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version.new"
     rm -rf "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE"
+    rm -rf "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalized"
     mkdir "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE"
+    if [ "$DEVELOPMENT" = true ]; then
+      mkdir "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalized"
+    fi
     if [ -n "$ARCHIVE" ]; then
       announce "Extracting $1: $ARCHIVE"
       tar -C "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" -xf "$SORTIX_MIRROR_DIR/$PACKAGE/$ARCHIVE" --strip-components=1
+      if [ "$DEVELOPMENT" = true ]; then
+        tar -C "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalized" -xf "$SORTIX_MIRROR_DIR/$PACKAGE/$ARCHIVE" --strip-components=1
+      fi
       if [ -n "$ARCHIVE_2" ]; then
         announce "Extracting $1: $ARCHIVE_2"
         tar -C "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" -xf "$SORTIX_MIRROR_DIR/$PACKAGE/$ARCHIVE_2" --strip-components=1
+        if [ "$DEVELOPMENT" = true ]; then
+          tar -C "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalized" -xf "$SORTIX_MIRROR_DIR/$PACKAGE/$ARCHIVE_2" --strip-components=1
+        fi
       fi
     fi
     if [ -f "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.patch" ]; then
-      patch -d "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" -p1 < "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.patch"
+      if [ "$DEVELOPMENT" = true ]; then
+        # TODO: .rej .orig etc.
+        patch -d "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" -p1 < "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.patch" || true
+        # .orig files aren't useful unless part of the patch got rejected.
+        find "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" \
+          -name '*.orig' \
+          -exec sh -c 'test ! -e "$(echo "$0" | sed -E "s,\\.orig$,.rej,")"' \
+          '{}' ';' -delete
+       else
+        patch -d "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" -p1 < "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.patch"
+       fi
     fi
     if [ -f "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.execpatch" ]; then
       tix-execpatch --directory "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.execpatch"
     fi
     if [ -f "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalize" ]; then
       tix-rmpatch --directory "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalize"
+      if [ "$DEVELOPMENT" = true ]; then
+        tix-rmpatch --directory "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalized" "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.normalize"
+      fi
     fi
-    if [ "$NEED_WRITABLE" != true ]; then
+    if [ "$DEVELOPMENT" != true -a "$NEED_WRITABLE" != true ]; then
       find "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" '!' -type d -exec chmod -w '{}' +
     fi
     mv "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version.new" "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version"
+    if [ "$DEVELOPMENT" = true ]; then
+       REJECTS="$(find "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE" \
+                       -name '*.rej' -o -name '*.orig' | sort)"
+       if [ -n "$REJECTS" ]; then
+         echo "$REJECTS"
+         echo "error: $PACKAGE: The above patch hunks were rejected"
+         exit 1
+       fi
+    fi
   fi
 )}
 
@@ -353,26 +417,29 @@ for PACKAGE in $PACKAGES; do
   SOURCE_PACKAGE=$( (SOURCE_PACKAGE= &&
                      . $SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.info &&
                      echo "$SOURCE_PACKAGE") )
+  DEVELOPMENT=$( (DEVELOPMENT= &&
+                  . $SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.info &&
+                  echo "$DEVELOPMENT") )
   # TODO: clean support.
 
-  if [ ! -f "$SORTIX_REPOSITORY_DIR/$PACKAGE.tix.tar.xz" ] ||
-     [ "$OPERATION" != build ] ; then
+  # download
+  if [ -n "$SOURCE_PACKAGE" ]; then
+    download_package "$SOURCE_PACKAGE"
+  fi
+  download_package "$PACKAGE"
+  if [ "$OPERATION" = download ]; then continue; fi
 
-    # download
-    if [ -n "$SOURCE_PACKAGE" ]; then
-      download_package "$SOURCE_PACKAGE"
-    fi
-    download_package "$PACKAGE"
-    if [ "$OPERATION" = download ]; then continue; fi
+  # extract
+  if [ -n "$SOURCE_PACKAGE" ]; then
+    extract_package "$SOURCE_PACKAGE"
+  fi
+  extract_package "$PACKAGE"
+  if [ "$OPERATION" = extract ]; then continue; fi
 
-    # extract
-    if [ -n "$SOURCE_PACKAGE" ]; then
-      extract_package "$SOURCE_PACKAGE"
-    fi
-    extract_package "$PACKAGE"
-    if [ "$OPERATION" = extract ]; then continue; fi
-
-    # build
+  # build
+  if [ ! -f "$SORTIX_REPOSITORY_DIR/$PACKAGE.tix.tar.xz" -o \
+       "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version" -nt \
+       "$SORTIX_REPOSITORY_DIR/$PACKAGE.tix.tar.xz" ]; then
     announce "Building $PACKAGE"
     tix-build \
       --sysroot="$SYSROOT" \
@@ -383,6 +450,10 @@ for PACKAGE in $PACKAGES; do
       ${SOURCE_PACKAGE:+--source-package "$SORTIX_PORTS_DIR/$SOURCE_PACKAGE/$SOURCE_PACKAGE"} \
       "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE"
     strip_tix "$SORTIX_REPOSITORY_DIR/$PACKAGE.tix.tar.xz"
+    if [ "$DEVELOPMENT" = true ]; then
+      # TODO: .rej .orig etc.
+      diff_package "$PACKAGE"
+    fi
   fi
   announce "Installing $PACKAGE"
   tix-install \
diff --git a/build-aux/clean-ports.sh b/build-aux/clean-ports.sh
index 716e3819..f76b9b89 100755
--- a/build-aux/clean-ports.sh
+++ b/build-aux/clean-ports.sh
@@ -34,6 +34,9 @@ get_all_packages() {
 
 # Clean all the packages.
 for PACKAGE in $(get_all_packages); do
+  DEVELOPMENT=$( (DEVELOPMENT= &&
+                  . $SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.info &&
+                  echo "$DEVELOPMENT") )
   if [ -e "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version" -o \
        -e "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version.new" ]; then
     tix-build \
@@ -44,6 +47,14 @@ for PACKAGE in $(get_all_packages); do
       --start=clean \
       --end=clean \
       "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE"
+    if [ "$DEVELOPMENT" = true ]; then
+      case "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE.version" in
+      *.development)
+        echo "Port is in development: '$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE'"
+        continue
+        ;;
+      esac
+    fi
     # TODO: New top-level makefile target for this.
     echo "Removing '$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE'"
     rm -rf "$SORTIX_PORTS_DIR/$PACKAGE/$PACKAGE"