repack: move `write_filtered_pack()` out of the builtin

In a similar fashion as in previous commits, move the function
`write_filtered_pack()` out of the builtin and into its own compilation
unit.

This function is now part of the repack.h API, but implemented in its
own "repack-filtered.c" unit as it is a separate component from other
kinds of repacking operations.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -1137,6 +1137,7 @@ LIB_OBJS += refs/ref-cache.o
 LIB_OBJS += refspec.o
 LIB_OBJS += remote.o
 LIB_OBJS += repack.o
+LIB_OBJS += repack-filtered.o
 LIB_OBJS += repack-geometry.o
 LIB_OBJS += repack-midx.o
 LIB_OBJS += repack-promisor.o

builtin/repack.c

@@ -106,52 +106,6 @@ static int repack_config(const char *var, const char *value,
 	return git_default_config(var, value, ctx, cb);
 }
 
-static int write_filtered_pack(const struct write_pack_opts *opts,
-			       struct existing_packs *existing,
-			       struct string_list *names)
-{
-	struct child_process cmd = CHILD_PROCESS_INIT;
-	struct string_list_item *item;
-	FILE *in;
-	int ret;
-	const char *caret;
-	const char *pack_prefix = write_pack_opts_pack_prefix(opts);
-
-	prepare_pack_objects(&cmd, opts->po_args, opts->destination);
-
-	strvec_push(&cmd.args, "--stdin-packs");
-
-	for_each_string_list_item(item, &existing->kept_packs)
-		strvec_pushf(&cmd.args, "--keep-pack=%s", item->string);
-
-	cmd.in = -1;
-
-	ret = start_command(&cmd);
-	if (ret)
-		return ret;
-
-	/*
-	 * Here 'names' contains only the pack(s) that were just
-	 * written, which is exactly the packs we want to keep. Also
-	 * 'existing_kept_packs' already contains the packs in
-	 * 'keep_pack_list'.
-	 */
-	in = xfdopen(cmd.in, "w");
-	for_each_string_list_item(item, names)
-		fprintf(in, "^%s-%s.pack\n", pack_prefix, item->string);
-	for_each_string_list_item(item, &existing->non_kept_packs)
-		fprintf(in, "%s.pack\n", item->string);
-	for_each_string_list_item(item, &existing->cruft_packs)
-		fprintf(in, "%s.pack\n", item->string);
-	caret = opts->po_args->pack_kept_objects ? "" : "^";
-	for_each_string_list_item(item, &existing->kept_packs)
-		fprintf(in, "%s%s.pack\n", caret, item->string);
-	fclose(in);
-
-	return finish_pack_objects_cmd(existing->repo->hash_algo, opts, &cmd,
-				       names);
-}
-
 static void combine_small_cruft_packs(FILE *in, size_t combine_cruft_below_size,
 				      struct existing_packs *existing)
 {

meson.build

@@ -463,6 +463,7 @@ libgit_sources = [
   'reftable/writer.c',
   'remote.c',
   'repack.c',
+  'repack-filtered.c',
   'repack-geometry.c',
   'repack-midx.c',
   'repack-promisor.c',

repack-filtered.c

@@ -0,0 +1,51 @@
+#include "git-compat-util.h"
+#include "repack.h"
+#include "repository.h"
+#include "run-command.h"
+#include "string-list.h"
+
+int write_filtered_pack(const struct write_pack_opts *opts,
+			struct existing_packs *existing,
+			struct string_list *names)
+{
+	struct child_process cmd = CHILD_PROCESS_INIT;
+	struct string_list_item *item;
+	FILE *in;
+	int ret;
+	const char *caret;
+	const char *pack_prefix = write_pack_opts_pack_prefix(opts);
+
+	prepare_pack_objects(&cmd, opts->po_args, opts->destination);
+
+	strvec_push(&cmd.args, "--stdin-packs");
+
+	for_each_string_list_item(item, &existing->kept_packs)
+		strvec_pushf(&cmd.args, "--keep-pack=%s", item->string);
+
+	cmd.in = -1;
+
+	ret = start_command(&cmd);
+	if (ret)
+		return ret;
+
+	/*
+	 * Here 'names' contains only the pack(s) that were just
+	 * written, which is exactly the packs we want to keep. Also
+	 * 'existing_kept_packs' already contains the packs in
+	 * 'keep_pack_list'.
+	 */
+	in = xfdopen(cmd.in, "w");
+	for_each_string_list_item(item, names)
+		fprintf(in, "^%s-%s.pack\n", pack_prefix, item->string);
+	for_each_string_list_item(item, &existing->non_kept_packs)
+		fprintf(in, "%s.pack\n", item->string);
+	for_each_string_list_item(item, &existing->cruft_packs)
+		fprintf(in, "%s.pack\n", item->string);
+	caret = opts->po_args->pack_kept_objects ? "" : "^";
+	for_each_string_list_item(item, &existing->kept_packs)
+		fprintf(in, "%s%s.pack\n", caret, item->string);
+	fclose(in);
+
+	return finish_pack_objects_cmd(existing->repo->hash_algo, opts, &cmd,
+				       names);
+}

repack.h

@@ -133,4 +133,8 @@ struct repack_write_midx_opts {
 void midx_snapshot_refs(struct repository *repo, struct tempfile *f);
 int write_midx_included_packs(struct repack_write_midx_opts *opts);
 
+int write_filtered_pack(const struct write_pack_opts *opts,
+			struct existing_packs *existing,
+			struct string_list *names);
+
 #endif /* REPACK_H */