[PATCH 12/18] receive-pack: print --pack-header directly into argv array

[Jeff King]

After receive-pack reads the pack header from the client, it
feeds the already-read part to index-pack and unpack-objects
via their --pack-header command-line options.  To do so, we
format it into a fixed buffer, then duplicate it into the
child's argv_array.

Our buffer is long enough to handle any possible input, so
this isn't wrong. But it's more complicated than it needs to
be; we can just argv_array_pushf() the final value and avoid
the intermediate copy. This drops the magic number and is
more efficient, too.

Note that we need to push to the argv_array in order, which
means we can't do the push until we are in the "unpack-objects
versus index-pack" conditional.  Rather than duplicate the
slightly complicated format specifier, I pushed it into a
helper function.

Signed-off-by: Jeff King <p...@peff.net>
---
 builtin/receive-pack.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index fb2a090a0..2ca93adef 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1634,12 +1634,17 @@ static const char *parse_pack_header(struct pack_header 
*hdr)
 
 static const char *pack_lockfile;
 
+static void push_header_arg(struct argv_array *args, struct pack_header *hdr)
+{
+       argv_array_pushf(args, "--pack_header=%"PRIu32",%"PRIu32,
+                       ntohl(hdr->hdr_version), ntohl(hdr->hdr_entries));
+}
+
 static const char *unpack(int err_fd, struct shallow_info *si)
 {
        struct pack_header hdr;
        const char *hdr_err;
        int status;
-       char hdr_arg[38];
        struct child_process child = CHILD_PROCESS_INIT;
        int fsck_objects = (receive_fsck_objects >= 0
                            ? receive_fsck_objects
@@ -1653,9 +1658,6 @@ static const char *unpack(int err_fd, struct shallow_info 
*si)
                        close(err_fd);
                return hdr_err;
        }
-       snprintf(hdr_arg, sizeof(hdr_arg),
-                       "--pack_header=%"PRIu32",%"PRIu32,
-                       ntohl(hdr.hdr_version), ntohl(hdr.hdr_entries));
 
        if (si->nr_ours || si->nr_theirs) {
                alt_shallow_file = setup_temporary_shallow(si->shallow);
@@ -1679,7 +1681,8 @@ static const char *unpack(int err_fd, struct shallow_info 
*si)
        tmp_objdir_add_as_alternate(tmp_objdir);
 
        if (ntohl(hdr.hdr_entries) < unpack_limit) {
-               argv_array_pushl(&child.args, "unpack-objects", hdr_arg, NULL);
+               argv_array_push(&child.args, "unpack-objects");
+               push_header_arg(&child.args, &hdr);
                if (quiet)
                        argv_array_push(&child.args, "-q");
                if (fsck_objects)
@@ -1697,8 +1700,8 @@ static const char *unpack(int err_fd, struct shallow_info 
*si)
        } else {
                char hostname[256];
 
-               argv_array_pushl(&child.args, "index-pack",
-                                "--stdin", hdr_arg, NULL);
+               argv_array_pushl(&child.args, "index-pack", "--stdin", NULL);
+               push_header_arg(&child.args, &hdr);
 
                if (gethostname(hostname, sizeof(hostname)))
                        xsnprintf(hostname, sizeof(hostname), "localhost");
-- 
2.12.2.845.g55fcf8b10