Fix picking default syntax for comments

[pikinier20]

Recently, there was a PR merged that changed -comment-syntax setting in Scaladoc to PathBased. It introduced a small regression in our docs: https://dotty.epfl.ch/api/index.html. The problem was that when we didn't find an entry that matched the path, we were always using default syntax which is Markdown. What we actually need to do is try to find a fallback entry (one without path specified) and use its syntax. Only if there's no such entry, we should fall back to Markdown.

[jchyb]

Looks great, thank you for fixing this! My only fear it that I am unsure if the original issue - the fact that despite 'docroot.txt' being in 'scala-library-src' it did not have the 'scala-library-src' syntax applied - was fixed.

[pikinier20]

Looks great, thank you for fixing this! My only fear it that I am unsure if the original issue - the fact that despite 'docroot.txt' being in 'scala-library-src' it did not have the 'scala-library-src' syntax applied - was fixed.

The problem that you mentioned is related to different thing. This file is treated differently than other source files. Its content is read and then parsed in context of top-level package. The top-level package doesn't have corresponding source file. Therefore, the default syntax was picked.

[jchyb]

Ah, makes sense. Thanks