Stick with the following style:
* Header 1 with the module name is in `lowercase`.
* Other headers are in `Sentence case`. Common header names that should
be consistently used are `Aliases`, `Contributing`, `Functions`,
`Settings`, and `Zsh options`.
* The names `Zim` and `Zsh` always appear capitalized, even in the
middle of sentences.
* Prefer
print 'code indented with 4 spaces'
instead of
```zsh
print 'code fenced by lines with three back-ticks'
print 'unless you want syntax highlighting'
```
so it behaves alike the non-verbose mode. For example, in the "merge"
special action context, files are being reported as both indexed and
unindexed by `git diff-index` and `git diff-files` commands in
non-verbose mode. That was not the case with the regular expressions
used in the verbose mode.
that, when defined, will be set if branch is both ahead and behind of
remote. If not defined, the `ahead` and `behind` contexts will still be
set, as how they worked previously.
based on the Prezto git module
[function](https://github.com/sorin-ionescu/prezto/blob/master/modules/git/functions/git-info)
and further refactored and simplified.
What changed:
- Commit format only in 'detached HEAD' state, so
`$(coalesce "%b" "%c")` is not needed, because you only get one of
those.
- Removed the `added`, `deleted`, `modified`, `renamed` and `unmerged`
verbose contexts.
- `git status` is only used in verbose mode.
- In non-verbose mode, the `untracked` context is not available, and
also untracked files are not considered for computing the `dirty`
context. Using `git status` or checking for untracked files is
[expensive](https://gist.github.com/sindresorhus/3898739).
