[PATCH v2 2/4] pack-write: refactor renaming in finish_tmp_packfile()

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

Refactor the renaming in finish_tmp_packfile() so that it takes a
"const struct strbuf *" instead of a non-const, and refactor the
repetitive renaming pattern in finish_tmp_packfile() to use a new
static rename_tmp_packfile() helper function.

The previous strbuf_reset() idiom originated with
5889271114a (finish_tmp_packfile():use strbuf for pathname
construction, 2014-03-03), which in turn was a minimal adjustment of
pre-strbuf code added in 0e990530ae (finish_tmp_packfile(): a helper
function, 2011-10-28).

Since the memory allocation is not a bottleneck here we can afford a
bit more readability at the cost of re-allocating this new "struct
strbuf sb".

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/pack-objects.c |  8 ++++++--
 pack-write.c           | 41 +++++++++++++++++++----------------------
 pack.h                 |  2 +-
 3 files changed, 26 insertions(+), 25 deletions(-)

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index df49f656b9..f2569b5ca2 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1250,7 +1250,10 @@ static void write_pack_file(void)
 					    &pack_idx_opts, hash);
 
 			if (write_bitmap_index) {
-				strbuf_addf(&tmpname, "%s.bitmap", hash_to_hex(hash));
+				struct strbuf sb = STRBUF_INIT;
+
+				strbuf_addf(&sb, "%s%s.bitmap", tmpname.buf,
+					    hash_to_hex(hash));
 
 				stop_progress(&progress_state);
 
@@ -1258,8 +1261,9 @@ static void write_pack_file(void)
 				bitmap_writer_select_commits(indexed_commits, indexed_commits_nr, -1);
 				bitmap_writer_build(&to_pack);
 				bitmap_writer_finish(written_list, nr_written,
-						     tmpname.buf, write_bitmap_options);
+						     sb.buf, write_bitmap_options);
 				write_bitmap_index = 0;
+				strbuf_release(&sb);
 			}
 
 			strbuf_release(&tmpname);
diff --git a/pack-write.c b/pack-write.c
index 277c60165e..363b395d67 100644
--- a/pack-write.c
+++ b/pack-write.c
@@ -462,7 +462,21 @@ struct hashfile *create_tmp_packfile(char **pack_tmp_name)
 	return hashfd(fd, *pack_tmp_name);
 }
 
-void finish_tmp_packfile(struct strbuf *name_buffer,
+static void rename_tmp_packfile(const char *source,
+				 const struct strbuf *basename,
+				 const unsigned char hash[],
+				 const char *ext)
+{
+	struct strbuf sb = STRBUF_INIT;
+
+	strbuf_addf(&sb, "%s%s.%s", basename->buf, hash_to_hex(hash), ext);
+	if (rename(source, sb.buf))
+		die_errno("unable to rename temporary '*.%s' file to '%s'",
+			  ext, sb.buf);
+	strbuf_release(&sb);
+}
+
+void finish_tmp_packfile(const struct strbuf *basename,
 			 const char *pack_tmp_name,
 			 struct pack_idx_entry **written_list,
 			 uint32_t nr_written,
@@ -470,7 +484,6 @@ void finish_tmp_packfile(struct strbuf *name_buffer,
 			 unsigned char hash[])
 {
 	const char *idx_tmp_name, *rev_tmp_name = NULL;
-	int basename_len = name_buffer->len;
 
 	if (adjust_shared_perm(pack_tmp_name))
 		die_errno("unable to make temporary pack file readable");
@@ -483,26 +496,10 @@ void finish_tmp_packfile(struct strbuf *name_buffer,
 	rev_tmp_name = write_rev_file(NULL, written_list, nr_written, hash,
 				      pack_idx_opts->flags);
 
-	strbuf_addf(name_buffer, "%s.pack", hash_to_hex(hash));
-
-	if (rename(pack_tmp_name, name_buffer->buf))
-		die_errno("unable to rename temporary pack file");
-
-	strbuf_setlen(name_buffer, basename_len);
-
-	if (rev_tmp_name) {
-		strbuf_addf(name_buffer, "%s.rev", hash_to_hex(hash));
-		if (rename(rev_tmp_name, name_buffer->buf))
-			die_errno("unable to rename temporary reverse-index file");
-
-		strbuf_setlen(name_buffer, basename_len);
-	}
-
-	strbuf_addf(name_buffer, "%s.idx", hash_to_hex(hash));
-	if (rename(idx_tmp_name, name_buffer->buf))
-		die_errno("unable to rename temporary index file");
-
-	strbuf_setlen(name_buffer, basename_len);
+	rename_tmp_packfile(pack_tmp_name, basename, hash, "pack");
+	if (rev_tmp_name)
+		rename_tmp_packfile(rev_tmp_name, basename, hash, "rev");
+	rename_tmp_packfile(idx_tmp_name, basename, hash, "idx");
 
 	free((void *)idx_tmp_name);
 }
diff --git a/pack.h b/pack.h
index 1c17254c0a..594d5176aa 100644
--- a/pack.h
+++ b/pack.h
@@ -110,7 +110,7 @@ int encode_in_pack_object_header(unsigned char *hdr, int hdr_len,
 int read_pack_header(int fd, struct pack_header *);
 
 struct hashfile *create_tmp_packfile(char **pack_tmp_name);
-void finish_tmp_packfile(struct strbuf *name_buffer,
+void finish_tmp_packfile(const struct strbuf *basename,
 			 const char *pack_tmp_name,
 			 struct pack_idx_entry **written_list,
 			 uint32_t nr_written,
-- 
2.33.0.819.gea1b153a43c