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

From: Derrick Stolee <redacted>

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 <redacted>
---
 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
 --------