[PATCH 5/9] archive-tar.c: move internal gzip implementation to a function

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Refactor the code added in 76d7602631a (archive-tar: add internal gzip
implementation, 2022-06-15) to call the magic "git archive gzip"
command as a function.

A subsequent commit will start using this as a fallback, but for now
there's no functional changes here.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 archive-tar.c | 43 +++++++++++++++++++++++++------------------
 1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/archive-tar.c b/archive-tar.c
index 8c5de949c64..dfc133deac7 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -465,12 +465,33 @@ static void tgz_write_block(const void *data)
 
 static const char internal_gzip_command[] = "git archive gzip";
 
-static int write_tar_filter_archive(const struct archiver *ar,
-				    struct archiver_args *args)
+static int gzip_internally(const struct archiver *ar,
+			   struct archiver_args *args)
 {
 #if ZLIB_VERNUM >= 0x1221
 	struct gz_header_s gzhead = { .os = 3 }; /* Unix, for reproducibility */
 #endif
+	int r;
+
+	write_block = tgz_write_block;
+	git_deflate_init_gzip(&gzstream, args->compression_level);
+#if ZLIB_VERNUM >= 0x1221
+	if (deflateSetHeader(&gzstream.z, &gzhead) != Z_OK)
+		BUG("deflateSetHeader() called too late");
+#endif
+	gzstream.next_out = outbuf;
+	gzstream.avail_out = sizeof(outbuf);
+
+	r = write_tar_archive(ar, args);
+
+	tgz_deflate(Z_FINISH);
+	git_deflate_end(&gzstream);
+	return r;
+}
+
+static int write_tar_filter_archive(const struct archiver *ar,
+				    struct archiver_args *args)
+{
 	struct strbuf cmd = STRBUF_INIT;
 	struct child_process filter = CHILD_PROCESS_INIT;
 	int r;
@@ -478,22 +499,8 @@ static int write_tar_filter_archive(const struct archiver *ar,
 	if (!ar->filter_command)
 		BUG("tar-filter archiver called with no filter defined");
 
-	if (!strcmp(ar->filter_command, internal_gzip_command)) {
-		write_block = tgz_write_block;
-		git_deflate_init_gzip(&gzstream, args->compression_level);
-#if ZLIB_VERNUM >= 0x1221
-		if (deflateSetHeader(&gzstream.z, &gzhead) != Z_OK)
-			BUG("deflateSetHeader() called too late");
-#endif
-		gzstream.next_out = outbuf;
-		gzstream.avail_out = sizeof(outbuf);
-
-		r = write_tar_archive(ar, args);
-
-		tgz_deflate(Z_FINISH);
-		git_deflate_end(&gzstream);
-		return r;
-	}
+	if (!strcmp(ar->filter_command, internal_gzip_command))
+		return gzip_internally(ar, args);
 
 	strbuf_addstr(&cmd, ar->filter_command);
 	if (args->compression_level >= 0)
-- 
2.39.1.1392.g63e6d408230