diff -urpa rpm-4.5.orig/build/parsePrep.c rpm-4.5/build/parsePrep.c
--- rpm-4.5.orig/build/parsePrep.c	2007-11-08 00:26:48.000000000 +0000
+++ rpm-4.5/build/parsePrep.c	2018-02-23 11:51:54.161446282 +0000
@@ -189,11 +189,13 @@ static const char *doUntar(Spec spec, in
 {
     const char *fn, *Lurlfn;
     static char buf[BUFSIZ];
-    char *taropts;
+    char taropts[8];
     char *t = NULL;
     struct Source *sp;
     rpmCompressedMagic compressed = COMPRESSED_NOT;
     int urltype;
+    const char *tar;
+    int rubygem = 0;
 
     for (sp = spec->sources; sp != NULL; sp = sp->next) {
 	if ((sp->flags & RPMFILE_SOURCE) && (sp->num == c)) {
@@ -205,8 +207,18 @@ static const char *doUntar(Spec spec, in
 	return NULL;
     }
 
+    t = strrchr(sp->source, '.');
+    if(t && !strcasecmp(t, ".gem"))
+	rubygem = 1;
+
+    t = stpcpy(taropts, "-x");
     /*@-internalglobs@*/ /* FIX: shrug */
-    taropts = ((rpmIsVerbose() && !quietly) ? "-xvvf" : "-xf");
+    if(rpmIsVerbose() && !quietly)
+	t = stpcpy(t, "vv");
+    if(rubygem)
+	t = stpcpy(t, "m");
+
+    t = stpcpy(t, "f");
     /*@=internalglobs@*/
 
     Lurlfn = rpmGenPath(NULL, "%{_sourcedir}/", sp->source);
@@ -233,6 +245,12 @@ static const char *doUntar(Spec spec, in
 	/*@notreached@*/ break;
     }
 
+    tar = rpmGetPath("%{?__tar}", NULL);
+    if (!(tar && *tar != '\0')) {
+	tar = _free(tar);
+	tar = xstrdup("tar");
+    }
+
     if (compressed != COMPRESSED_NOT) {
 	const char *zipper;
 	int needtar = 1;
@@ -267,8 +285,13 @@ static const char *doUntar(Spec spec, in
 	*t++ = '\'';
 	t = stpcpy(t, fn);
 	*t++ = '\'';
-	if (needtar)
-	    t = stpcpy( stpcpy( stpcpy(t, " | tar "), taropts), " -");
+	if (needtar) {
+	    t = stpcpy(t, " | ");
+	    t = stpcpy(t, tar);
+	    t = stpcpy(t, " ");
+	    t = stpcpy(t, taropts);
+	    t = stpcpy(t, " -");
+	}
 	t = stpcpy(t,
 		"\n"
 		"STATUS=$?\n"
@@ -277,11 +300,24 @@ static const char *doUntar(Spec spec, in
 		"fi");
     } else {
 	buf[0] = '\0';
-	t = stpcpy( stpcpy(buf, "tar "), taropts);
+	t = stpcpy(buf, tar);
+	t = stpcpy(t, " ");
+	t = stpcpy(t, taropts);
 	*t++ = ' ';
 	t = stpcpy(t, fn);
+	if(rubygem) {
+	    t = stpcpy(t,
+		    "\n"
+		    "if [ -f data.tar.gz ]; then\n"
+		    "  tar ");
+            t = stpcpy(t, taropts);
+	    t = stpcpy(t,
+		    " data.tar.gz\n"
+		    "fi");
+	}
     }
 
+    tar = _free(tar);
     Lurlfn = _free(Lurlfn);
     return buf;
 }
@@ -390,6 +426,20 @@ static int doSetupMacro(Spec spec, char
 	appendLineStringBuf(spec->prep, buf);
     }
 
+    /* check if source is a ruby gem */
+    {   struct Source *sp;
+	for (sp = spec->sources; sp != NULL; sp = sp->next) {
+	    if ((sp->flags & RPMFILE_SOURCE) && (sp->num == 0)) {
+		break;
+	    }
+	}
+	if (sp != NULL) {
+	    char *t = strrchr(sp->source, '.');
+	    if(t && !strcasecmp(t, ".gem"))
+		createDir = 1;
+	}
+    }
+
     /* if necessary, create and cd into the proper dir */
     if (createDir) {
 	sprintf(buf, MKDIR_P " '%s'\ncd '%s'",