You have many questions here, but I'd like to answer the main one: 
How do I rename a folder in a GitHub private repo from the git shell
Folders are not tracked directly, but the files within them are tracked based on the pathway. If you have an empty folder that you wish to rename, you would first have to add a file to that folder. It will then be trackable. 
I know you mentioned you're on Windows, but I'll show you what this looks like on OS X: 
bash-3.2$ ls
archetypes  config.yaml data        public
config.toml content     posts       themes
bash-3.2$ git status
On branch master
nothing to commit, working directory clean
bash-3.2$ ls posts/
404.html                page
apple-touch-icon-144-precomposed.png    page.html
css                 posts
favicon.png             posts.html
index.html              sitemap.xml
index.xml               touch-icon-144-precomposed.png
js
bash-3.2$ mv posts/ posts_other/
bash-3.2$ ls
archetypes  config.yaml data        public
config.toml content     posts_other themes
bash-3.2$ git status
On branch master
Changes not staged for commit:
    deleted:    posts/.html
    deleted:    posts/404.html
    deleted:    posts/apple-touch-icon-144-precomposed.png
    deleted:    posts/css/highlight/arta.css
    deleted:    posts/css/highlight/ascetic.css
    deleted:    posts/css/highlight/atelier-dune.dark.css
    deleted:    posts/css/highlight/atelier-dune.light.css
    deleted:    posts/css/highlight/atelier-forest.dark.css
    deleted:    posts/css/highlight/atelier-forest.light.css
    deleted:    posts/css/highlight/atelier-heath.dark.css
    deleted:    posts/css/highlight/atelier-heath.light.css
    deleted:    posts/css/highlight/atelier-lakeside.dark.css
    deleted:    posts/css/highlight/atelier-lakeside.light.css
    deleted:    posts/css/highlight/atelier-seaside.dark.css
    deleted:    posts/css/highlight/atelier-seaside.light.css
    deleted:    posts/css/highlight/codepen-embed.css
    deleted:    posts/css/highlight/color-brewer.css
    deleted:    posts/css/highlight/dark.css
    deleted:    posts/css/highlight/default.css
    deleted:    posts/css/highlight/docco.css
    deleted:    posts/css/highlight/far.css
    deleted:    posts/css/highlight/foundation.css
    deleted:    posts/css/highlight/github.css
    deleted:    posts/css/highlight/googlecode.css
    deleted:    posts/css/highlight/hybrid.css
    deleted:    posts/css/highlight/idea.css
    deleted:    posts/css/highlight/ir_black.css
    deleted:    posts/css/highlight/kimbie.dark.css
    deleted:    posts/css/highlight/kimbie.light.css
    deleted:    posts/css/highlight/magula.css
    deleted:    posts/css/highlight/mono-blue.css
    deleted:    posts/css/highlight/monokai.css
    deleted:    posts/css/highlight/monokai_sublime.css
    deleted:    posts/css/highlight/obsidian.css
    deleted:    posts/css/highlight/paraiso.dark.css
    deleted:    posts/css/highlight/paraiso.light.css
    deleted:    posts/css/highlight/railscasts.css
    deleted:    posts/css/highlight/rainbow.css
    deleted:    posts/css/highlight/solarized_dark.css
    deleted:    posts/css/highlight/solarized_light.css
    deleted:    posts/css/highlight/sunburst.css
    deleted:    posts/css/highlight/tomorrow-night-blue.css
    deleted:    posts/css/highlight/tomorrow-night-bright.css
    deleted:    posts/css/highlight/tomorrow-night-eighties.css
    deleted:    posts/css/highlight/tomorrow-night.css
    deleted:    posts/css/highlight/tomorrow.css
    deleted:    posts/css/highlight/vs.css
    deleted:    posts/css/highlight/xcode.css
    deleted:    posts/css/highlight/zenburn.css
    deleted:    posts/css/hyde-overrides.css
    deleted:    posts/css/hyde-x.css
    deleted:    posts/css/hyde.css
    deleted:    posts/css/poole-overrides.css
    deleted:    posts/css/poole.css
    deleted:    posts/css/syntax.css
    deleted:    posts/favicon.png
    deleted:    posts/index.html
    deleted:    posts/index.xml
    deleted:    posts/js/highlight.pack.js
    deleted:    posts/page.html
    deleted:    posts/page/1.html
    deleted:    posts/posts.html
    deleted:    posts/posts/first.html
    deleted:    posts/posts/first/index.html
    deleted:    posts/posts/index.html
    deleted:    posts/posts/index.xml
    deleted:    posts/sitemap.xml
    deleted:    posts/touch-icon-144-precomposed.png
Untracked files:
    posts_other/
no changes added to commit
bash-3.2$ git add posts_other/
bash-3.2$ git status
On branch master
Changes to be committed:
    new file:   posts_other/.html
    new file:   posts_other/404.html
    new file:   posts_other/apple-touch-icon-144-precomposed.png
    new file:   posts_other/css/highlight/arta.css
    new file:   posts_other/css/highlight/ascetic.css
    new file:   posts_other/css/highlight/atelier-dune.dark.css
    new file:   posts_other/css/highlight/atelier-dune.light.css
    new file:   posts_other/css/highlight/atelier-forest.dark.css
    new file:   posts_other/css/highlight/atelier-forest.light.css
    new file:   posts_other/css/highlight/atelier-heath.dark.css
    new file:   posts_other/css/highlight/atelier-heath.light.css
    new file:   posts_other/css/highlight/atelier-lakeside.dark.css
    new file:   posts_other/css/highlight/atelier-lakeside.light.css
    new file:   posts_other/css/highlight/atelier-seaside.dark.css
    new file:   posts_other/css/highlight/atelier-seaside.light.css
    new file:   posts_other/css/highlight/codepen-embed.css
    new file:   posts_other/css/highlight/color-brewer.css
    new file:   posts_other/css/highlight/dark.css
    new file:   posts_other/css/highlight/default.css
    new file:   posts_other/css/highlight/docco.css
    new file:   posts_other/css/highlight/far.css
    new file:   posts_other/css/highlight/foundation.css
    new file:   posts_other/css/highlight/github.css
    new file:   posts_other/css/highlight/googlecode.css
    new file:   posts_other/css/highlight/hybrid.css
    new file:   posts_other/css/highlight/idea.css
    new file:   posts_other/css/highlight/ir_black.css
    new file:   posts_other/css/highlight/kimbie.dark.css
    new file:   posts_other/css/highlight/kimbie.light.css
    new file:   posts_other/css/highlight/magula.css
    new file:   posts_other/css/highlight/mono-blue.css
    new file:   posts_other/css/highlight/monokai.css
    new file:   posts_other/css/highlight/monokai_sublime.css
    new file:   posts_other/css/highlight/obsidian.css
    new file:   posts_other/css/highlight/paraiso.dark.css
    new file:   posts_other/css/highlight/paraiso.light.css
    new file:   posts_other/css/highlight/railscasts.css
    new file:   posts_other/css/highlight/rainbow.css
    new file:   posts_other/css/highlight/solarized_dark.css
    new file:   posts_other/css/highlight/solarized_light.css
    new file:   posts_other/css/highlight/sunburst.css
    new file:   posts_other/css/highlight/tomorrow-night-blue.css
    new file:   posts_other/css/highlight/tomorrow-night-bright.css
    new file:   posts_other/css/highlight/tomorrow-night-eighties.css
    new file:   posts_other/css/highlight/tomorrow-night.css
    new file:   posts_other/css/highlight/tomorrow.css
    new file:   posts_other/css/highlight/vs.css
    new file:   posts_other/css/highlight/xcode.css
    new file:   posts_other/css/highlight/zenburn.css
    new file:   posts_other/css/hyde-overrides.css
    new file:   posts_other/css/hyde-x.css
    new file:   posts_other/css/hyde.css
    new file:   posts_other/css/poole-overrides.css
    new file:   posts_other/css/poole.css
    new file:   posts_other/css/syntax.css
    new file:   posts_other/favicon.png
    new file:   posts_other/index.html
    new file:   posts_other/index.xml
    new file:   posts_other/js/highlight.pack.js
    new file:   posts_other/page.html
    new file:   posts_other/page/1.html
    new file:   posts_other/posts.html
    new file:   posts_other/posts/first.html
    new file:   posts_other/posts/first/index.html
    new file:   posts_other/posts/index.html
    new file:   posts_other/posts/index.xml
    new file:   posts_other/sitemap.xml
    new file:   posts_other/touch-icon-144-precomposed.png
Changes not staged for commit:
    deleted:    posts/.html
    deleted:    posts/404.html
    deleted:    posts/apple-touch-icon-144-precomposed.png
    deleted:    posts/css/highlight/arta.css
    deleted:    posts/css/highlight/ascetic.css
    deleted:    posts/css/highlight/atelier-dune.dark.css
    deleted:    posts/css/highlight/atelier-dune.light.css
    deleted:    posts/css/highlight/atelier-forest.dark.css
    deleted:    posts/css/highlight/atelier-forest.light.css
    deleted:    posts/css/highlight/atelier-heath.dark.css
    deleted:    posts/css/highlight/atelier-heath.light.css
    deleted:    posts/css/highlight/atelier-lakeside.dark.css
    deleted:    posts/css/highlight/atelier-lakeside.light.css
    deleted:    posts/css/highlight/atelier-seaside.dark.css
    deleted:    posts/css/highlight/atelier-seaside.light.css
    deleted:    posts/css/highlight/codepen-embed.css
    deleted:    posts/css/highlight/color-brewer.css
    deleted:    posts/css/highlight/dark.css
    deleted:    posts/css/highlight/default.css
    deleted:    posts/css/highlight/docco.css
    deleted:    posts/css/highlight/far.css
    deleted:    posts/css/highlight/foundation.css
    deleted:    posts/css/highlight/github.css
    deleted:    posts/css/highlight/googlecode.css
    deleted:    posts/css/highlight/hybrid.css
    deleted:    posts/css/highlight/idea.css
    deleted:    posts/css/highlight/ir_black.css
    deleted:    posts/css/highlight/kimbie.dark.css
    deleted:    posts/css/highlight/kimbie.light.css
    deleted:    posts/css/highlight/magula.css
    deleted:    posts/css/highlight/mono-blue.css
    deleted:    posts/css/highlight/monokai.css
    deleted:    posts/css/highlight/monokai_sublime.css
    deleted:    posts/css/highlight/obsidian.css
    deleted:    posts/css/highlight/paraiso.dark.css
    deleted:    posts/css/highlight/paraiso.light.css
    deleted:    posts/css/highlight/railscasts.css
    deleted:    posts/css/highlight/rainbow.css
    deleted:    posts/css/highlight/solarized_dark.css
    deleted:    posts/css/highlight/solarized_light.css
    deleted:    posts/css/highlight/sunburst.css
    deleted:    posts/css/highlight/tomorrow-night-blue.css
    deleted:    posts/css/highlight/tomorrow-night-bright.css
    deleted:    posts/css/highlight/tomorrow-night-eighties.css
    deleted:    posts/css/highlight/tomorrow-night.css
    deleted:    posts/css/highlight/tomorrow.css
    deleted:    posts/css/highlight/vs.css
    deleted:    posts/css/highlight/xcode.css
    deleted:    posts/css/highlight/zenburn.css
    deleted:    posts/css/hyde-overrides.css
    deleted:    posts/css/hyde-x.css
    deleted:    posts/css/hyde.css
    deleted:    posts/css/poole-overrides.css
    deleted:    posts/css/poole.css
    deleted:    posts/css/syntax.css
    deleted:    posts/favicon.png
    deleted:    posts/index.html
    deleted:    posts/index.xml
    deleted:    posts/js/highlight.pack.js
    deleted:    posts/page.html
    deleted:    posts/page/1.html
    deleted:    posts/posts.html
    deleted:    posts/posts/first.html
    deleted:    posts/posts/first/index.html
    deleted:    posts/posts/index.html
    deleted:    posts/posts/index.xml
    deleted:    posts/sitemap.xml
    deleted:    posts/touch-icon-144-precomposed.png
bash-3.2$ git add .
bash-3.2$ git commit -m "Renamed post repository to posts_other"
[master 073ed6250b97] Renamed post repository to posts_other
 68 files changed, 0 insertions(+), 0 deletions(-)
 rename {posts => posts_other}/.html (100%)
 rename {posts => posts_other}/404.html (100%)
 rename {posts => posts_other}/apple-touch-icon-144-precomposed.png (100%)
 rename {posts => posts_other}/css/highlight/arta.css (100%)
 rename {posts => posts_other}/css/highlight/ascetic.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-dune.dark.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-dune.light.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-forest.dark.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-forest.light.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-heath.dark.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-heath.light.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-lakeside.dark.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-lakeside.light.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-seaside.dark.css (100%)
 rename {posts => posts_other}/css/highlight/atelier-seaside.light.css (100%)
 rename {posts => posts_other}/css/highlight/codepen-embed.css (100%)
 rename {posts => posts_other}/css/highlight/color-brewer.css (100%)
 rename {posts => posts_other}/css/highlight/dark.css (100%)
 rename {posts => posts_other}/css/highlight/default.css (100%)
 rename {posts => posts_other}/css/highlight/docco.css (100%)
 rename {posts => posts_other}/css/highlight/far.css (100%)
 rename {posts => posts_other}/css/highlight/foundation.css (100%)
 rename {posts => posts_other}/css/highlight/github.css (100%)
 rename {posts => posts_other}/css/highlight/googlecode.css (100%)
 rename {posts => posts_other}/css/highlight/hybrid.css (100%)
 rename {posts => posts_other}/css/highlight/idea.css (100%)
 rename {posts => posts_other}/css/highlight/ir_black.css (100%)
 rename {posts => posts_other}/css/highlight/kimbie.dark.css (100%)
 rename {posts => posts_other}/css/highlight/kimbie.light.css (100%)
 rename {posts => posts_other}/css/highlight/magula.css (100%)
 rename {posts => posts_other}/css/highlight/mono-blue.css (100%)
 rename {posts => posts_other}/css/highlight/monokai.css (100%)
 rename {posts => posts_other}/css/highlight/monokai_sublime.css (100%)
 rename {posts => posts_other}/css/highlight/obsidian.css (100%)
 rename {posts => posts_other}/css/highlight/paraiso.dark.css (100%)
 rename {posts => posts_other}/css/highlight/paraiso.light.css (100%)
 rename {posts => posts_other}/css/highlight/railscasts.css (100%)
 rename {posts => posts_other}/css/highlight/rainbow.css (100%)
 rename {posts => posts_other}/css/highlight/solarized_dark.css (100%)
 rename {posts => posts_other}/css/highlight/solarized_light.css (100%)
 rename {posts => posts_other}/css/highlight/sunburst.css (100%)
 rename {posts => posts_other}/css/highlight/tomorrow-night-blue.css (100%)
 rename {posts => posts_other}/css/highlight/tomorrow-night-bright.css (100%)
 rename {posts => posts_other}/css/highlight/tomorrow-night-eighties.css (100%)
 rename {posts => posts_other}/css/highlight/tomorrow-night.css (100%)
 rename {posts => posts_other}/css/highlight/tomorrow.css (100%)
 rename {posts => posts_other}/css/highlight/vs.css (100%)
 rename {posts => posts_other}/css/highlight/xcode.css (100%)
 rename {posts => posts_other}/css/highlight/zenburn.css (100%)
 rename {posts => posts_other}/css/hyde-overrides.css (100%)
 rename {posts => posts_other}/css/hyde-x.css (100%)
 rename {posts => posts_other}/css/hyde.css (100%)
 rename {posts => posts_other}/css/poole-overrides.css (100%)
 rename {posts => posts_other}/css/poole.css (100%)
 rename {posts => posts_other}/css/syntax.css (100%)
 rename {posts => posts_other}/favicon.png (100%)
 rename {posts => posts_other}/index.html (100%)
 rename {posts => posts_other}/index.xml (100%)
 rename {posts => posts_other}/js/highlight.pack.js (100%)
 rename {posts => posts_other}/page.html (100%)
 rename {posts => posts_other}/page/1.html (100%)
 rename {posts => posts_other}/posts.html (100%)
 rename {posts => posts_other}/posts/first.html (100%)
 rename {posts => posts_other}/posts/first/index.html (100%)
 rename {posts => posts_other}/posts/index.html (100%)
 rename {posts => posts_other}/posts/index.xml (100%)
 rename {posts => posts_other}/sitemap.xml (100%)
 rename {posts => posts_other}/touch-icon-144-precomposed.png (100%)
bash-3.2$ 
In regards to your problems sharing code between Windows & Linux, there are very good tutorials on the matter. Here is what I used and I also refer to this blog. 
Most importantly, make sure to set your text attributes wisely as this other question answers (because CRLF is a jerk).