builtin/refs: add optimize subcommand

As part of the ongoing effort to consolidate reference handling,
introduce a new `optimize` subcommand. This command provides the same
functionality and exit-code behavior as `git pack-refs`, serving as its
modern replacement.

Implement `cmd_refs_optimize` by having it call the `pack_refs_core()`
helper function. This helper was factored out of the original
`cmd_pack_refs` in a preceding commit, allowing both commands to share
the same core logic as independent peers.

Add documentation for the new command. The man page leverages the shared
options file, created in a previous commit, by using the AsciiDoc
`include::` macro to ensure consistency with git-pack-refs(1).

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: shejialuo <shejialuo@gmail.com>
Signed-off-by: Meet Soni <meetsoni3017@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-refs.adoc

@@ -18,6 +18,7 @@ git refs list [--count=<count>] [--shell|--perl|--python|--tcl]
 		   [--contains[=<object>]] [--no-contains[=<object>]]
 		   [(--exclude=<pattern>)...] [--start-after=<marker>]
 		   [ --stdin | (<pattern>...)]
+git refs optimize [--all] [--no-prune] [--auto] [--include <pattern>] [--exclude <pattern>]
 
 DESCRIPTION
 -----------
@@ -38,6 +39,11 @@ list::
 	formatting, and sorting. This subcommand is an alias for
 	linkgit:git-for-each-ref[1] and offers identical functionality.
 
+optimize::
+	Optimizes references to improve repository performance and reduce disk
+	usage. This subcommand is an alias for linkgit:git-pack-refs[1] and
+	offers identical functionality.
+
 OPTIONS
 -------
 
@@ -73,6 +79,10 @@ The following options are specific to 'git refs list':
 
 include::for-each-ref-options.adoc[]
 
+The following options are specific to 'git refs optimize':
+
+include::pack-refs-options.adoc[]
+
 KNOWN LIMITATIONS
 -----------------