Add description/abstract
Add staging by patch reset command
Combine treeish/commitish with understanding overview
Nest all submodule/subtree topics under one heading
Add comments for each `gh` command
Remove API topics until further examples available
Combine difftool and mergtool section under one heading
Correct reset patch capitalization
Add additional examples and resource of commitish
Fix Releases summary sub-heading level
Cleanup dup branch content, tidy bullet objectives
Rearrange order of commit diagrams
Amalgamate rebase -i cherry-pick into one bullet
Combine remotes and refspect
Remove extraneous white space at end of line
Revert "Remove API topics until further examples available"

This reverts commit 02ca9ca0cdaee93053f2de95b64dcb6d43b2aa3f.
Merge pull request #188 from github/curriculum-advanced-tune-up

Update/tune Advanced deck section, content, headings