autogen: add sanity checks for git submodules

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>

autogen.pl

@@ -1,6 +1,6 @@
 #!/usr/bin/env perl
 #
-# Copyright (c) 2009-2017 Cisco Systems, Inc.  All rights reserved
+# Copyright (c) 2009-2019 Cisco Systems, Inc.  All rights reserved
 # Copyright (c) 2010      Oracle and/or its affiliates.  All rights reserved.
 # Copyright (c) 2013      Mellanox Technologies, Inc.
 #                         All rights reserved.
@@ -1231,6 +1231,54 @@ $step. Checking tool versions\n\n";
 
 #---------------------------------------------------------------------------
 
+++$step;
+verbose "\n$step. Checking for git submodules\n\n";
+
+# Make sure we got a submodule-full clone.  If not, abort and let a
+# human figure it out.
+if (-f ".gitmodules") {
+    open(IN, "git submodule status|")
+        || die "Can't run \"git submodule status\"";
+    while (<IN>) {
+        chomp;
+        $_ =~ m/^(.)(.{40}) ([^ ]+) *\(*([^\(\)]*)\)*$/;
+        my $status     = $1;
+        my $local_hash = $2;
+        my $path       = $3;
+        my $extra      = $4;
+
+        print("=== Submodule: $path\n");
+
+        # Make sure the submodule is there
+        if ($status eq "-") {
+            print("    ==> ERROR: Missing
+
+The submodule \"$path\" is missing.
+
+Perhaps you forgot to \"git clone --recursive ...\", or you need to
+\"git submodule update --init --recursive\"...?\n\n");
+            exit(1);
+        }
+
+        # See if the submodule is at the expected git hash
+        # (it may be ok if it's not -- just warn the user)
+        $extra =~ m/-g(.+)/;
+        my $remote_hash = $1;
+        if ($remote_hash) {
+            my $abbrev_local_hash = substr($local_hash, 0, length($remote_hash));
+            if ($remote_hash ne $abbrev_local_hash) {
+                print("    ==> WARNING: Submodule hash is different than upstream.
+         If this is not intentional, you may want to run:
+         \"git submodule update --init --recursive\"\n");
+            } else {
+                print("    Local hash == remote hash (good!)\n");
+            }
+        }
+    }
+}
+
+#---------------------------------------------------------------------------
+
 # Save the platform file in the m4
 $m4 .= "dnl Platform file\n";