index-pack: add a helper function to derive .idx/.keep filename

These are automatically named by replacing .pack suffix in the
name of the packfile.  Add a small helper to do so, as I'll be
adding another one soonish.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 285424f3d4ed66e4d9ae18abedbb4ab04948fa21..a5588a24d1c528d5b4e69aece48ead4aee9e3355 100644 (file)
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -1598,6 +1598,18 @@ static void show_pack_info(int stat_only)
        }
 }
 
+static const char *derive_filename(const char *pack_name, const char *suffix,
+                                  struct strbuf *buf)
+{
+       size_t len;
+       if (!strip_suffix(pack_name, ".pack", &len))
+               die(_("packfile name '%s' does not end with '.pack'"),
+                   pack_name);
+       strbuf_add(buf, pack_name, len);
+       strbuf_addstr(buf, suffix);
+       return buf->buf;
+}
+
 int cmd_index_pack(int argc, const char **argv, const char *prefix)
 {
        int i, fix_thin_pack = 0, verify = 0, stat_only = 0;
@@ -1706,24 +1718,11 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
                usage(index_pack_usage);
        if (fix_thin_pack && !from_stdin)
                die(_("--fix-thin cannot be used without --stdin"));
-       if (!index_name && pack_name) {
-               size_t len;
-               if (!strip_suffix(pack_name, ".pack", &len))
-                       die(_("packfile name '%s' does not end with '.pack'"),
-                           pack_name);
-               strbuf_add(&index_name_buf, pack_name, len);
-               strbuf_addstr(&index_name_buf, ".idx");
-               index_name = index_name_buf.buf;
-       }
-       if (keep_msg && !keep_name && pack_name) {
-               size_t len;
-               if (!strip_suffix(pack_name, ".pack", &len))
-                       die(_("packfile name '%s' does not end with '.pack'"),
-                           pack_name);
-               strbuf_add(&keep_name_buf, pack_name, len);
-               strbuf_addstr(&keep_name_buf, ".keep");
-               keep_name = keep_name_buf.buf;
-       }
+       if (!index_name && pack_name)
+               index_name = derive_filename(pack_name, ".idx", &index_name_buf);
+       if (keep_msg && !keep_name && pack_name)
+               keep_name = derive_filename(pack_name, ".keep", &keep_name_buf);
+
        if (verify) {
                if (!index_name)
                        die(_("--verify with no packfile name given"));