Fix #4090 by escaping filename page/img link (without path) for short link

[sapk]

And add more tests

[techknowlogick]

Comment to link issue to PR #4090

[techknowlogick]

CI fail. I restarted Drone, but same fail happened. Looks like it is related to this change.

[lafriks]

Seems to me it breaks links like path/name.jpg as it escapes also / characters

[sapk]

@lafriks You are totally right!
I first think of removing it for image link but choose to only url-encode when we have only a filename like [[Test?#]]. The user could still use the format [[some/path/Test?#|some/path/Test%3F%23]] for advanced use cases.

[codecov-io]

Codecov Report

Merging #4091 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4091      +/-   ##
==========================================
- Coverage   19.96%   19.96%   -0.01%     
==========================================
  Files         153      153              
  Lines       30521    30524       +3     
==========================================
  Hits         6094     6094              
- Misses      23513    23515       +2     
- Partials      914      915       +1

Impacted Files	Coverage Δ
modules/markup/html.go	79.9% <100%> (+0.14%)	⬆️
modules/process/manager.go	69.56% <0%> (-4.35%)	⬇️

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[lafriks]

Or probably you can escape only last part by splitting /

[sapk]

@lafriks I think of it but I didn't go that way as I find it kind of strange to encode only part of the url and a other solution could be to encode all except /.
I did some testing on github to know how they do it and I find that they encode all url and translate / in - and that they don't do support [[ ]] in issue comment but doing so may break how we do it and previous link.

So I choose a simple implementation only supporting filename without path but I can change if needed.

[lafriks]

I would prefer to have behaviour same as GitHub so that imported/mirrored GitHub wiki/md would work same also on Gitea but that probably can be done in other PR

[lunny]

@sapk please send a back port to v1.4