builtin/config: introduce "remove-section" subcommand

Introduce a new "remove-section" subcommand to git-config(1). Please
refer to preceding commits regarding the motivation behind this change.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-config.txt

@@ -14,7 +14,7 @@ SYNOPSIS
 'git config set' [<file-option>] [--type=<type>] [--all] [--value=<value>] [--fixed-value] <name> <value>
 'git config unset' [<file-option>] [--all] [--value=<value>] [--fixed-value] <name> <value>
 'git config rename-section' [<file-option>] <old-name> <new-name>
-'git config' [<file-option>] --remove-section <name>
+'git config remove-section' [<file-option>] <name>
 'git config' [<file-option>] --get-colorbool <name> [<stdout-is-tty>]
 'git config' [<file-option>] -e | --edit
 
@@ -95,6 +95,9 @@ unset::
 rename-section::
 	Rename the given section to a new name.
 
+remove-section::
+	Remove the given section from the configuration file.
+
 [[OPTIONS]]
 OPTIONS
 -------
@@ -192,9 +195,6 @@ See also <<FILES>>.
 	section in linkgit:gitrevisions[7] for a more complete list of
 	ways to spell blob names.
 
---remove-section::
-	Remove the given section from the configuration file.
-
 --fixed-value::
 	When used with the `value-pattern` argument, treat `value-pattern` as
 	an exact string instead of a regular expression. This will restrict
@@ -333,6 +333,9 @@ recommended to migrate to the new syntax.
 --rename-section <old-name> <new-name>::
 	Replaced by `git config rename-section <old-name> <new-name>`.
 
+--remove-section <name>::
+	Replaced by `git config remove-section <name>`.
+
 CONFIGURATION
 -------------
 `pager.config` is only respected when listing configuration, i.e., when