/usr/share/gps/show_coverage.xsl is in gnat-gps-common 5.3dfsg-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82  | <?xml version="1.0" ?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
  <xsl:output method="html"/>
<xsl:template match="/">
  <html>
    <head>
      <title><xsl:value-of select="Code_Analysis_Tree/@name"/></title>
      <style type="text/css">
.Project {color:blue}
.File {text-indent:5px}
.Subprogram {color:grey; text-indent:10px}
      </style>
    </head>
    <body>
      <table border="1">
        <tr><th>Entities</th><th>Coverage</th><th>Percentage</th></tr>
        <xsl:apply-templates select="*"/>
      </table>
    </body>
  </html>
</xsl:template>
<xsl:template match="Code_Analysis_Tree|vfs_name|Line">
  <xsl:apply-templates select="*"/>
</xsl:template>
<xsl:template match="Project|Subprogram">
  <tr class="{name()}">
    <td><xsl:value-of select="@name"/></td>
    <td>
      <xsl:value-of select="@children"/>
      <xsl:text> lines (</xsl:text>
      <xsl:value-of select="@coverage"/>
      <xsl:text> not covered)</xsl:text>
    </td>
    <td>
      <xsl:value-of select=
         "format-number(number(@coverage) * 100 div number(@children),'#')"/>
    </td>
  </tr>
  <xsl:apply-templates select="*"/>
</xsl:template>
<xsl:template match="File[@status='FILE_NOT_FOUND']"/>
<xsl:template match="File[@status='VALID']">
  <tr class="{name()}">
    <td>
      <xsl:call-template name="file-name">
        <xsl:with-param name="path" select="vfs_name/text()"/>
      </xsl:call-template>
    </td>
    <td>
      <xsl:value-of select="@children"/>
      <xsl:text> lines (</xsl:text>
      <xsl:value-of select="@coverage"/>
      <xsl:text> not covered)</xsl:text>
    </td>
    <td>
      <xsl:value-of select=
         "format-number(number(@coverage) * 100 div number(@children),'#')"/>
    </td>
  </tr>
  <xsl:apply-templates select="*"/>
</xsl:template>
<xsl:template name="file-name">
  <xsl:param name="path"/>
  <xsl:if test="contains ($path, '/')">
    <xsl:call-template name="file-name">
      <xsl:with-param name="path" select="substring-after($path, '/')"/>
    </xsl:call-template>
  </xsl:if>
  <xsl:if test="not (contains ($path, '/'))">
    <xsl:value-of select="$path"/>
  </xsl:if>
</xsl:template>
</xsl:stylesheet>
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