ps/stash-in-c, was Re: What's cooking in git.git (Mar 2019, #01; Wed, 6)

> * ps/stash-in-c (2019-03-01) 28 commits
>  - tests: add a special setup where stash.useBuiltin is off
>  - stash: optionally use the scripted version again
>  - stash: add back the original, scripted `git stash`
>  - stash: convert `stash--helper.c` into `stash.c`
>  - stash: replace all `write-tree` child processes with API calls
>  - stash: optimize `get_untracked_files()` and `check_changes()`
>  - stash: convert save to builtin
>  - stash: make push -q quiet
>  - stash: convert push to builtin
>  - stash: convert create to builtin
>  - stash: convert store to builtin
>  - stash: convert show to builtin
>  - stash: convert list to builtin
>  - stash: convert pop to builtin
>  - stash: convert branch to builtin
>  - stash: convert drop and clear to builtin
>  - stash: convert apply to builtin
>  - stash: mention options in `show` synopsis
>  - stash: add tests for `git stash show` config
>  - stash: rename test cases to be more descriptive
>  - t3903: add test for --intent-to-add file
>  - t3903: modernize style
>  - stash: improve option parsing test coverage
>  - ident: add the ability to provide a "fallback identity"
>  - strbuf.c: add `strbuf_insertf()` and `strbuf_vinsertf()`
>  - strbuf.c: add `strbuf_join_argv()`
>  - sha1-name.c: add `get_oidf()` which acts like `get_oid()`
>  - Merge branch 'sd/stash-wo-user-name'
> 
>  "git stash" rewritten in C.
> 
>  Will merge to 'next'.