This patch makes the UUIDs in the XMP header optional, depending on the
setting of the environment variable GS_GENERATE_UUIDS.

If the environment variable GS_GENERATE_UUIDS is set to "0" or "no", it will
not write out the Document UUID field and also will write the Instance ID
field value as "".

Upstream does not want to do this.

See: https://bugs.ghostscript.com/show_bug.cgi?id=698208
diff -ur orig/gnu-ghostscript-9.14.0/devices/vector/gdevpdfe.c aa/gnu-ghostscript-9.14.0/devices/vector/gdevpdfe.c
--- orig/gnu-ghostscript-9.14.0/devices/vector/gdevpdfe.c	2017-07-09 23:30:28.960479189 +0200
+++ gnu-ghostscript-9.14.0/devices/vector/gdevpdfe.c	2017-07-10 01:04:12.252478276 +0200
@@ -620,7 +620,7 @@
         return code;
 
     /* PDF/A XMP reference recommends setting UUID to empty. If not empty must be a URI */
-    if (pdev->PDFA != 0)
+    if (pdev->PDFA != 0 || (getenv("GS_GENERATE_UUIDS") && (strcasecmp(getenv("GS_GENERATE_UUIDS"), "0") == 0 || strcasecmp(getenv("GS_GENERATE_UUIDS"), "no") == 0)))
         instance_uuid[0] = 0x00;
 
     cre_date_time_len = pdf_get_docinfo_item(pdev, "/CreationDate", cre_date_time, sizeof(cre_date_time));
@@ -720,14 +720,17 @@
             pdf_xml_tag_close(s, "rdf:Description");
             pdf_xml_newline(s);
 
-            pdf_xml_tag_open_beg(s, "rdf:Description");
-            pdf_xml_copy(s, " rdf:about=\"\"");
-            pdf_xml_attribute_name(s, "xmlns:xapMM");
-            pdf_xml_attribute_value(s, "http://ns.adobe.com/xap/1.0/mm/");
-            pdf_xml_attribute_name(s, "xapMM:DocumentID");
-            pdf_xml_attribute_value(s, document_uuid);
-            pdf_xml_tag_end_empty(s);
-            pdf_xml_newline(s);
+            if (!getenv("GS_GENERATE_UUIDS") || (strcasecmp(getenv("GS_GENERATE_UUIDS"), "0") != 0 && strcasecmp(getenv("GS_GENERATE_UUIDS"), "no") != 0))
+            {
+                pdf_xml_tag_open_beg(s, "rdf:Description");
+                pdf_xml_copy(s, " rdf:about=\"\"");
+                pdf_xml_attribute_name(s, "xmlns:xapMM");
+                pdf_xml_attribute_value(s, "http://ns.adobe.com/xap/1.0/mm/");
+                pdf_xml_attribute_name(s, "xapMM:DocumentID");
+                pdf_xml_attribute_value(s, document_uuid);
+                pdf_xml_tag_end_empty(s);
+                pdf_xml_newline(s);
+            }
 
             pdf_xml_tag_open_beg(s, "rdf:Description");
             pdf_xml_copy(s, " rdf:about=\"\"");
cessing.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/image-processing.scm?id=823997e969718efd6ab56fca7a9aae3f458ba978&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2017-06-03 18:19:07 +0200'>2017-06-03</span></td><td><a href='/guix/commit/gnu/packages/image-processing.scm?id=98d6cdda37721ca950732aec272f6e004c402959'>gnu: Remove old vtk module dependence in image-processing.scm.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-processing.scm: Remove old vtk module dependence.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2017-06-02 18:47:06 +0200'>2017-06-02</span></td><td><a href='/guix/commit/gnu/packages/image-processing.scm?id=fb226b43511671bee3463a02eea9e041d2610fef'>gnu: Move vtk to image-processing.scm.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-processing.scm (vtk): New variable.
* gnu/packages/vtk.scm: Delete file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Remove it.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>John Darrington</td></tr>
<tr><td><span title='2017-05-15 21:34:09 +0200'>2017-05-15</span></td><td><a href='/guix/commit/gnu/packages/image-processing.scm?id=cdb2a21160a195f63c33955d8b9b9034e11dae46'>gnu: Add mia.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-processing.scm (mia): New variable.

Co-authored-by: Ricardo Wurmus &lt;rekado@elephly.net&gt;
</span></span></td><td>John Darrington</td></tr>
<tr><td><span title='2017-05-15 21:22:06 +0200'>2017-05-15</span></td><td><a href='/guix/commit/gnu/packages/image-processing.scm?id=504c285d1092c9b7a2ef25c7a436da02bef70dc2'>gnu: Add dcmtk.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/image-processing.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.

Co-authored-by: Ricardo Wurmus &lt;rekado@elephly.net&gt;
</span></span></td><td>John Darrington</td></tr>