ld/sparse-diff-blame, was What's cooking in git.git (Dec 2021, #02; Tue, 7)

[Lessley Dennington <lessleydennington@gmail.com>]

> * ld/sparse-diff-blame (2021-12-06) 8 commits
>   - blame: enable and test the sparse index
>   - diff: enable and test the sparse index
>   - diff: replace --staged with --cached in t1092 tests
>   - repo-settings: prepare_repo_settings only in git repos
>   - test-read-cache: set up repo after git directory
>   - commit-graph: return if there is no git directory
>   - git: ensure correct git directory setup with -h
>   - Merge branch 'vd/sparse-reset' into ld/sparse-diff-blame
>   (this branch is used by ds/fetch-pull-with-sparse-index; uses vd/sparse-reset.)
> 
>   Teach diff and blame to work well with sparse index.
> 
>   Will merge to 'next'?
>   source: <pull.1050.v6.git.1638806161.gitgitgadget@gmail.com>
> 

This series has been reviewed at different stages by:

Junio C Hamano <gitster@pobox.com>
	- Suggested addition of BUG in prepare_repo_settings.
	- Suggested --help fix for certain builtins when run outside repos
	  or with special config settings.
	- Suggested using --cached instead of --staged in diff tests.
Elijah Newren <newren@gmail.com>
	- Suggested diff commit message cleanup.
	- Corrected git commit message typo.
	- Corrected comment on blame sparse index tests specifying why
	  this builtin does not work on files outside the working
	  directory.
Ævar Arnfjörð Bjarmason <avarab@gmail.com>
	- Suggested lower case first letter in prepare_repo_settings BUG
	  message.
Taylor Blau <me@ttaylor.com>
	- Suggested diff/blame commit description cleanups
	- Suggested addition of more diff sparse index test cases
	- Suggested cleanup of blame sparse index test cases
	

I believe all comments have been addressed (either in the form of a
re-roll or a patch or explanation in my reply) and that this branch is
ready to merge to 'next'. I have cc'd all reviewers, though, in case there
was something I missed.

Lessley