Reduce overhead of upgrades for users with custom stylesheets/JS

[techknowlogick]

I have custom JS/CSS in use on my gitea instance and when I upgrade I have to edit head.tmpl and footer.tmpl to add in my changes again (otherwise I might have out of date templates). This will allow me to put all of my changes in header_extras.tmpl/footer_extras.tmpl and not worry about upgrading.

Open to suggestions regarding the names of the additional templates, or their locations.

[codecov-io]

Codecov Report

Merging #3051 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3051      +/-   ##
==========================================
- Coverage   33.43%   33.41%   -0.03%     
==========================================
  Files         270      270              
  Lines       39553    39553              
==========================================
- Hits        13226    13216      -10     
- Misses      24441    24447       +6     
- Partials     1886     1890       +4

Impacted Files	Coverage Δ
models/repo_indexer.go	45.54% <0%> (-3.47%)	⬇️
models/repo.go	37.96% <0%> (-0.19%)	⬇️

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[sapk]

A little change needed and add 2-3 lines (in https://github.com/go-gitea/gitea/blob/master/docs/content/doc/advanced/customizing-gitea.en-us.md) recommending to use extra folder to add some custom header and footer resources to keep template updated.

[sapk]

Cleaner to create a folder extra at root of templates containing footer.tmpl and header.tmpl.

[techknowlogick]

@sapk thanks for the feedback. I've changed the directory for the extras template files, and added in some documentation on when to use them.

[sapk]

LGTM

[ethantkoenig]

Would custom be a better directory name than extras?

[techknowlogick]

@ethantkoenig Thanks for feedback. As custom is already a top level dir, when we tell people to go to the custom folder it might create confusion to have multiple dirs with the same name. (See use of custom on this page: https://docs.gitea.io/en-us/customizing-gitea/ )

[ethantkoenig]

@techknowlogick Could we explicitly tell them to go to templates/custom, so they don't get confused?

[techknowlogick]

@ethantkoenig yes, but then for the other custom directory we have to explicitly say not the templates/custom directory. For example we have instructions for adding the robots.txt, and serving public files to put all of those in custom or custom/public. There is also a user on discord that is currently confused about just even the one custom directory.

However, this is as much commitment to the idea of that folder name as I have, and so in light of the above if you still want me to change the directory name I will.

[ethantkoenig]

I personally prefer custom over extras, for two reasons:

1. I think it more clearly describes the intent of the directory (customized template changes). If I saw the name extras, my first instinct would be that it is a directory of miscellaneous templates, not customizable ones.
2. For consistency with the existing custom directory; every directory named custom is for some sort of custom change.

[techknowlogick]

Ok. Sounds good. Im out right now, but will change it when I get home.

[techknowlogick]

@ethantkoenig I've updated it. Thanks again for the feedback.

cc: @lafriks

[lafriks]

LGTM