Re: [PATCH 03/11] config-batch: implement get v1

> From: Derrick Stolee <stolee@gmail.com>
> 
> The 'get' command for the 'git config-batch' builtin is the first command
> and is currently at version 1. It returns at most one value, the same as
> 'git config --get <key>' with optional value-based filtering.
> 
> The documentation and tests detail the specifics of how to format requests
> of this format and how to parse the results.
> 
> Future versions could consider multi-valued responses or regex-based key
> matching.
> 
> For the sake of incremental exploration of the potential in the 'git
> config-batch' command, this is the only implementation being presented in
> the first patch series.
> 
> Future extensions could include a '-z' parameter that uses NUL bytes in the
> command and output format to allow for spaces or newlines in the input or
> newlines in the output.
> 
> Signed-off-by: Derrick Stolee <stolee@gmail.com>
> ---
>  Documentation/git-config-batch.adoc |  53 +++++-
>  builtin/config-batch.c              | 251 +++++++++++++++++++++++++++-
>  config.h                            |   3 +
>  t/t1312-config-batch.sh             | 101 +++++++++++
>  4 files changed, 405 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/git-config-batch.adoc b/Documentation/git-config-batch.adoc
> index 9ca04b0c1e..31dd42f481 100644
> --- a/Documentation/git-config-batch.adoc
> +++ b/Documentation/git-config-batch.adoc
> @@ -32,9 +32,58 @@ set. Thus, if the Git version includes the `git config-batch` builtin
>  but doesn't understand an input command, it will return a single line
>  response:
>  
> -```
> +------------
>  unknown_command LF
> -```
> +------------
> +

> +These are the commands that are currently understood:
> +
> +`get` version 1::
> +	The `get` command searches the config key-value pairs within a
> +	given `<scope>` for values that match the fixed `<key>` and

> +	filters the resulting value based on an optional `<value-filter>`.
> +	This can either be a regex or a fixed value. The command format
> +	is one of the following formats:
> ++
> +------------
> +get 1 <scope> <key>
> +get 1 <scope> <key> arg:regex <value-pattern>
> +get 1 <scope> <key> arg:fixed-value <value>
> +------------
> ++

> +The `<scope>` value can be one of `inherited`, `system`, `global`,
> +`local`, `worktree`, `submodule`, or `command`. If `inherited`, then all
> +config key-value pairs will be considered regardless of scope. Otherwise,
> +only the given scope will be considered.
> ++
> +If no optional arguments are given, then the value will not be filtered
> +by any pattern matching. If `arg:regex` is specified, then the rest of
> +the line is considered a single string, `<value-pattern>`, and is
> +interpreted as a regular expression for matching against stored values,
> +similar to specifying a value to `get config --get <key> "<value-pattern>"`.
> +If `arg:fixed-value` is specified, then the rest of the line is
> +considered a single string, `<value>`, and is checked for an exact
> +match against the key-value pairs, simmilar to `git config --get <key>

> +pair in the standard config order by scope and sequence within each scope.
> ++
> +If a key-value pair is found, then the following output is given:
> ++
> +------------
> +get 1 found <key> <scope> <value>
> +------------
> ++
> +If no matching key-value pair is found, then the following output is
> +given:
> ++
> +------------
> +get 1 missing <key> [<value-pattern>|<value>]
> +------------
> ++

> +where `<value-pattern>` or `<value>` is only supplied if provided in
> +the command.
>  
>  SEE ALSO
>  --------