paper/coal: use fixed width for diffstat +/- link

The plus and minus characters are normally not the same width in a
non-monospace font, and this made the line length change when the
diffstat display was toggled.

The square brackets are not rendered in a monospace font to ensure
that they align with the parenthesis on the same line.

mercurial/templates/paper/changeset.tmpl

@@ -66,9 +66,9 b' files, or words in the commit message</d'
   <th class="diffstat">diffstat</th>
   <td class="diffstat">
     {diffsummary}
-    <a id="diffstatexpand" href="javascript:showDiffstat()"/>[+]</a>
+    <a id="diffstatexpand" href="javascript:showDiffstat()"/>[<tt>+</tt>]</a>
     <div id="diffstatdetails" style="display:none;">
-      <a href="javascript:hideDiffstat()"/>[-]</a>
+      <a href="javascript:hideDiffstat()"/>[<tt>-</tt>]</a>
       <p>
       <table>{diffstat}</table>
     </div>

tests/test-hgweb-commands.t

@@ -357,9 +357,9 b' Logs and changes'
     <td class="diffstat">
        2 files changed, 2 insertions(+), 0 deletions(-)
   
-      <a id="diffstatexpand" href="javascript:showDiffstat()"/>[+]</a>
+      <a id="diffstatexpand" href="javascript:showDiffstat()"/>[<tt>+</tt>]</a>
       <div id="diffstatdetails" style="display:none;">
-        <a href="javascript:hideDiffstat()"/>[-]</a>
+        <a href="javascript:hideDiffstat()"/>[<tt>-</tt>]</a>
         <p>
         <table>  <tr class="parity0">
       <td class="diffstat-file"><a href="#l1.1">da/foo</a></td>

tests/test-hgweb-diffs.t

@@ -99,9 +99,9 b' revision'
     <td class="diffstat">
        2 files changed, 2 insertions(+), 0 deletions(-)
   
-      <a id="diffstatexpand" href="javascript:showDiffstat()"/>[+]</a>
+      <a id="diffstatexpand" href="javascript:showDiffstat()"/>[<tt>+</tt>]</a>
       <div id="diffstatdetails" style="display:none;">
-        <a href="javascript:hideDiffstat()"/>[-]</a>
+        <a href="javascript:hideDiffstat()"/>[<tt>-</tt>]</a>
         <p>
         <table>  <tr class="parity0">
       <td class="diffstat-file"><a href="#l1.1">a</a></td>
@@ -359,9 +359,9 b' revision'
     <td class="diffstat">
        2 files changed, 2 insertions(+), 0 deletions(-)
   
-      <a id="diffstatexpand" href="javascript:showDiffstat()"/>[+]</a>
+      <a id="diffstatexpand" href="javascript:showDiffstat()"/>[<tt>+</tt>]</a>
       <div id="diffstatdetails" style="display:none;">
-        <a href="javascript:hideDiffstat()"/>[-]</a>
+        <a href="javascript:hideDiffstat()"/>[<tt>-</tt>]</a>
         <p>
         <table>  <tr class="parity0">
       <td class="diffstat-file"><a href="#l1.1">a</a></td>

tests/test-hgweb-removed.t

@@ -94,9 +94,9 b' revision'
     <td class="diffstat">
        1 files changed, 0 insertions(+), 1 deletions(-)
   
-      <a id="diffstatexpand" href="javascript:showDiffstat()"/>[+]</a>
+      <a id="diffstatexpand" href="javascript:showDiffstat()"/>[<tt>+</tt>]</a>
       <div id="diffstatdetails" style="display:none;">
-        <a href="javascript:hideDiffstat()"/>[-]</a>
+        <a href="javascript:hideDiffstat()"/>[<tt>-</tt>]</a>
         <p>
         <table>  <tr class="parity0">
       <td class="diffstat-file"><a href="#l1.1">a</a></td>