When navigating the themes tutorial (developer/howto/themes), the
rdtraining page wasn't clickable in the global toc, even though it was
specified as :show-content: (note that the rdtraining is only in 14.0+).
The heuristic extracting the pagename from a toctree node wasn't
considering the current depth if the page referenced by the toctree
node was in the same folder than the current page.
Explanation:
We are computing the toctree for the page developer/howtos/themes. One
of the toctree nodes references the rdtraining page, with a relative
link, i.e. `rdtraining.html`.
We were wrongfully looking for `show_content` in the metadata of the
`rdtraining` page, instead of `developer/howtos/rdtraining`, since we
didn't consider the current document depth when the reference didn't
contain any `/`.
This commit ensures that if the current document has a depth > 1, this
depth is currently considered, even for links referencing documents in
the same folder.
task-2538297
10612f0ba7