damaged (and duplicate) headings

[bugmenot]

It seems like add_information is damaging and partially duplicating existing headings on commons file description pages. See this example: <pre> == {{int:filedesc}} == description

== {{int:license-header}} == {{PD}}

[[Category:Media missing infobox template]] </pre>

gets

<pre> =={{int:filedesc}}== {{Information |Description = description |Source = |Date = |Author = |Permission = |other_versions = }}

{{int:filedesc}} == {{int:license-header}} == {{PD}} [[Category:Media missing infobox template]] </pre>

Note the missing "==" before {{int:filedesc}} and {{int:license-header}} as well as the duplication of {{int:filedesc}}

[bugmenot]

It happens for example if there was already a heading like == {{int:filedesc}} == on the description page.

[bugmenot]

also damages existing templates like {{check categories}} if there's a line break (between some but not all parameter fields?) by truncating at the line break.