doc: Don't hide the "Up" link when it is the same as "Home"

The original stylesheets seemed to think this was a good idea, but our
users find it confusing and unhelpful, so undo that logic.
Reported-by: Fabien COELHO <coelho@cri.ensmp.fr>
Discussion: https://www.postgresql.org/message-id/flat/alpine.DEB.2.22.394.2006210914370.859381%40pseudo

doc/src/sgml/stylesheet.xsl

@@ -57,7 +57,6 @@ Customization of header
   <xsl:variable name="row1" select="$navig.showtitles != 0"/>
   <xsl:variable name="row2" select="count($prev) &gt; 0
                                     or (count($up) &gt; 0
-                                        and generate-id($up) != generate-id($home)
                                         and $navig.showtitles != 0)
                                     or count($next) &gt; 0"/>
 
@@ -95,8 +94,7 @@ Customization of header
               </td>
               <td width="10%" align="{$direction.align.start}">
                 <xsl:choose>
-                  <xsl:when test="count($up)&gt;0
-                                  and generate-id($up) != generate-id($home)">
+                  <xsl:when test="count($up)&gt;0">
                     <a accesskey="u">
                       <xsl:attribute name="href">
                         <xsl:call-template name="href.target">
@@ -117,7 +115,6 @@ Customization of header
               <th width="60%" align="center">
                 <xsl:choose>
                   <xsl:when test="count($up) > 0
-                                  and generate-id($up) != generate-id($home)
                                   and $navig.showtitles != 0">
                     <xsl:apply-templates select="$up" mode="object.title.markup"/>
                   </xsl:when>
@@ -176,4 +173,162 @@ Customization of header
   </xsl:if>
 </xsl:template>
 
+
+<!--
+Customization of footer
+- don't hide redundant Up link
+- add tool tips to links
+
+(overrides html/chunk-common.xsl)
+-->
+<xsl:template name="footer.navigation">
+  <xsl:param name="prev" select="/foo"/>
+  <xsl:param name="next" select="/foo"/>
+  <xsl:param name="nav.context"/>
+
+  <xsl:variable name="home" select="/*[1]"/>
+  <xsl:variable name="up" select="parent::*"/>
+
+  <xsl:variable name="row1" select="count($prev) &gt; 0
+                                    or count($up) &gt; 0
+                                    or count($next) &gt; 0"/>
+
+  <xsl:variable name="row2" select="($prev and $navig.showtitles != 0)
+                                    or (generate-id($home) != generate-id(.)
+                                        or $nav.context = 'toc')
+                                    or ($chunk.tocs.and.lots != 0
+                                        and $nav.context != 'toc')
+                                    or ($next and $navig.showtitles != 0)"/>
+
+  <xsl:if test="$suppress.navigation = '0' and $suppress.footer.navigation = '0'">
+    <div class="navfooter">
+      <xsl:if test="$footer.rule != 0">
+        <hr/>
+      </xsl:if>
+
+      <xsl:if test="$row1 or $row2">
+        <table width="100%" summary="Navigation footer">
+          <xsl:if test="$row1">
+            <tr>
+              <td width="40%" align="{$direction.align.start}">
+                <xsl:if test="count($prev)>0">
+                  <a accesskey="p">
+                    <xsl:attribute name="href">
+                      <xsl:call-template name="href.target">
+                        <xsl:with-param name="object" select="$prev"/>
+                      </xsl:call-template>
+                    </xsl:attribute>
+                    <xsl:attribute name="title">
+                      <xsl:apply-templates select="$prev" mode="object.title.markup"/>
+                    </xsl:attribute>
+                    <xsl:call-template name="navig.content">
+                      <xsl:with-param name="direction" select="'prev'"/>
+                    </xsl:call-template>
+                  </a>
+                </xsl:if>
+                <xsl:text>&#160;</xsl:text>
+              </td>
+              <td width="20%" align="center">
+                <xsl:choose>
+                  <xsl:when test="count($up)&gt;0">
+                    <a accesskey="u">
+                      <xsl:attribute name="href">
+                        <xsl:call-template name="href.target">
+                          <xsl:with-param name="object" select="$up"/>
+                        </xsl:call-template>
+                      </xsl:attribute>
+                      <xsl:attribute name="title">
+                        <xsl:apply-templates select="$up" mode="object.title.markup"/>
+                      </xsl:attribute>
+                      <xsl:call-template name="navig.content">
+                        <xsl:with-param name="direction" select="'up'"/>
+                      </xsl:call-template>
+                    </a>
+                  </xsl:when>
+                  <xsl:otherwise>&#160;</xsl:otherwise>
+                </xsl:choose>
+              </td>
+              <td width="40%" align="{$direction.align.end}">
+                <xsl:text>&#160;</xsl:text>
+                <xsl:if test="count($next)>0">
+                  <a accesskey="n">
+                    <xsl:attribute name="href">
+                      <xsl:call-template name="href.target">
+                        <xsl:with-param name="object" select="$next"/>
+                      </xsl:call-template>
+                    </xsl:attribute>
+                    <xsl:attribute name="title">
+                      <xsl:apply-templates select="$next" mode="object.title.markup"/>
+                    </xsl:attribute>
+                    <xsl:call-template name="navig.content">
+                      <xsl:with-param name="direction" select="'next'"/>
+                    </xsl:call-template>
+                  </a>
+                </xsl:if>
+              </td>
+            </tr>
+          </xsl:if>
+
+          <xsl:if test="$row2">
+            <tr>
+              <td width="40%" align="{$direction.align.start}" valign="top">
+                <xsl:if test="$navig.showtitles != 0">
+                  <xsl:apply-templates select="$prev" mode="object.title.markup"/>
+                </xsl:if>
+                <xsl:text>&#160;</xsl:text>
+              </td>
+              <td width="20%" align="center">
+                <xsl:choose>
+                  <xsl:when test="$home != . or $nav.context = 'toc'">
+                    <a accesskey="h">
+                      <xsl:attribute name="href">
+                        <xsl:call-template name="href.target">
+                          <xsl:with-param name="object" select="$home"/>
+                        </xsl:call-template>
+                      </xsl:attribute>
+                      <xsl:attribute name="title">
+                        <xsl:apply-templates select="$home" mode="object.title.markup"/>
+                      </xsl:attribute>
+                      <xsl:call-template name="navig.content">
+                        <xsl:with-param name="direction" select="'home'"/>
+                      </xsl:call-template>
+                    </a>
+                    <xsl:if test="$chunk.tocs.and.lots != 0 and $nav.context != 'toc'">
+                      <xsl:text>&#160;|&#160;</xsl:text>
+                    </xsl:if>
+                  </xsl:when>
+                  <xsl:otherwise>&#160;</xsl:otherwise>
+                </xsl:choose>
+
+                <xsl:if test="$chunk.tocs.and.lots != 0 and $nav.context != 'toc'">
+                  <a accesskey="t">
+                    <xsl:attribute name="href">
+                      <xsl:value-of select="$chunked.filename.prefix"/>
+                      <xsl:apply-templates select="/*[1]"
+                                           mode="recursive-chunk-filename">
+                        <xsl:with-param name="recursive" select="true()"/>
+                      </xsl:apply-templates>
+                      <xsl:text>-toc</xsl:text>
+                      <xsl:value-of select="$html.ext"/>
+                    </xsl:attribute>
+                    <xsl:call-template name="gentext">
+                      <xsl:with-param name="key" select="'nav-toc'"/>
+                    </xsl:call-template>
+                  </a>
+                </xsl:if>
+              </td>
+              <td width="40%" align="{$direction.align.end}" valign="top">
+                <xsl:text>&#160;</xsl:text>
+                <xsl:if test="$navig.showtitles != 0">
+                  <xsl:apply-templates select="$next" mode="object.title.markup"/>
+                </xsl:if>
+              </td>
+            </tr>
+          </xsl:if>
+        </table>
+      </xsl:if>
+    </div>
+  </xsl:if>
+</xsl:template>
+
 </xsl:stylesheet>