Fix id replacements in SVGs with clipping paths.

This fixes `--embed-resources` when SVGs have `clip-path`
attributes.

Closes #9420.

Author: jgm

src/Text/Pandoc/SelfContained.hs

@@ -185,6 +185,10 @@ convertTags (t@(TagOpen tagname as):ts)
                             case T.uncons x of
                               Just ('#', x') -> (k, "#" <> svgid <> "_" <> x')
                               _ -> (k, x)
+                          addIdPrefix ("clip-path", x) = ("clip-path",
+                            case T.stripPrefix "url(#" x of
+                              Just x' -> "url(#" <> svgid <> "_" <> x'
+                              Nothing -> x)
                           addIdPrefix kv = kv
                       let ensureUniqueId (TagOpen tname ats) =
                             TagOpen tname (map addIdPrefix ats)

test/command/9420.md

@@ -0,0 +1,13 @@
+```
+% pandoc --embed-resources
+![](command/9420.svg)
+^D
+<p><svg id="svg_e1815ef374a63cf552e4" width="504pt" height="360pt" viewBox="0 0 504 360">
+<defs>
+<clipPath id="svg_e1815ef374a63cf552e4_clip1-c3ce354c">
+  <path />
+</clipPath>
+</defs>
+<g clip-path="url(#svg_e1815ef374a63cf552e4_clip1-c3ce354c)" clip-rule="nonzero"></g>
+</svg></p>
+```