Merge remote-tracking branch 'origin/topic/johanna/configure-check-su…

…bmodules'

* origin/topic/johanna/configure-check-submodules:
  Address review feedback for configure error change
  Raise configure error message for unsupported archives

configure

@@ -133,15 +133,33 @@ Usage: $0 [OPTION]... [VAR=VALUE]...
 
 sourcedir="$(cd "$(dirname "$0")" && pwd)"
 
-if [ ! -e "$sourcedir/cmake/COPYING" ] && [ -d "$sourcedir/.git" ]; then
-    echo "\
+if [ ! -e "$sourcedir/cmake/COPYING" ]; then
+    if [ -d "$sourcedir/.git" ]; then
+        echo "\
 You seem to be missing the content of the cmake directory.
 
 This typically means that you performed a non-recursive git clone of
 Zeek. To check out the required subdirectories, please execute:
 
   ( cd $sourcedir && git submodule update --recursive --init )
 " >&2
+    else
+        echo "\
+You seem to be missing the content of the cmake directory.
+
+This typically means that you downloaded a non-release archive from github.
+These archives do not contain all required files.
+
+If you want to download the current release of Zeek, please download a full
+archive using one of the links at https://zeek.org/get-zeek/.
+
+If you want to get the current development version of Zeek, please use git to
+clone our repository.
+
+See https://docs.zeek.org/en/master/install.html#retrieving-the-sources for
+instructions.
+" >&2
+    fi
     exit 1
 fi