Following your instructions, I created the _includes dir, copied the headers.html and do bundle info --path minima
to find my hidden theme files: C:\ruby26-x64\lib\ruby\gems\2.6.0\gems\minima-2.5.1 and copy the header.html (as you said, same as https://github.com/jekyll/minima/blob/master/_includes/header.html)
One problem is that the theme does not really work as they say in the documentation: https://github.com/jekyll/minima#customize-navigation-links (There is no header_pages: about.md in the _config.yml file which would be a great solution.)
Now, I’m stuck in the figuring it part. What should I use? I would like to delete the whole thing and just leave the part for the header, but I’m not quite sure. Here is the header.html code, without any comments
<header class="site-header">
<div class="wrapper">
{%- assign default_paths = site.pages | map: "path" -%}
{%- assign page_paths = site.header_pages | default: default_paths -%}
{%- assign titles_size = site.pages | map: 'title' | join: '' | size -%}
<a class="site-title" rel="author" href="{{ "/" | relative_url }}">{{ site.title | escape }}</a>
{%- if titles_size > 0 -%}
<nav class="site-nav">
<input type="checkbox" id="nav-trigger" class="nav-trigger" />
<label for="nav-trigger">
<span class="menu-icon">
<svg viewBox="0 0 18 15" width="18px" height="15px">
<path d="M18,1.484c0,0.82-0.665,1.484-1.484,1.484H1.484C0.665,2.969,0,2.304,0,1.484l0,0C0,0.665,0.665,0,1.484,0 h15.032C17.335,0,18,0.665,18,1.484L18,1.484z M18,7.516C18,8.335,17.335,9,16.516,9H1.484C0.665,9,0,8.335,0,7.516l0,0 c0-0.82,0.665-1.484,1.484-1.484h15.032C17.335,6.031,18,6.696,18,7.516L18,7.516z M18,13.516C18,14.335,17.335,15,16.516,15H1.484 C0.665,15,0,14.335,0,13.516l0,0c0-0.82,0.665-1.483,1.484-1.483h15.032C17.335,12.031,18,12.695,18,13.516L18,13.516z"/>
</svg>
</span>
</label>
<div class="trigger">
{%- for path in page_paths -%}
{%- assign my_page = site.pages | where: "path", path | first -%}
{%- if my_page.title -%}
<a class="page-link" href="{{ my_page.url | relative_url }}">{{ my_page.title | escape }}</a>
{%- endif -%}
{%- endfor -%}
</div>
</nav>
{%- endif -%}
When I commit the _includes/header.html the whole navbar disappears.