Add support for "forcing" a ref on the remote side

A "old ref" of all zeroes is considered a "don't care" ref, and allows
us to say "write the new ref regardless of what the old ref contained
(or even if it existed at all)".

This allows (if git-send-pack were to do it) creating new refs, and
fixing up old ones.

diff --git a/receive-pack.c b/receive-pack.c
index 7ce5f1e..0a3e012 100644 (file)
--- a/receive-pack.c
+++ b/receive-pack.c
@@ -97,11 +97,22 @@ struct command {
 
 struct command *commands = NULL;
 
+static int is_all_zeroes(const char *hex)
+{
+       int i;
+       for (i = 0; i < 40; i++)
+               if (*hex++ != '0')
+                       return 0;
+       return 1;
+}
+
 static int verify_old_ref(const char *name, char *hex_contents)
 {
        int fd, ret;
        char buffer[60];
 
+       if (is_all_zeroes(hex_contents))
+               return 0;
        fd = open(name, O_RDONLY);
        if (fd < 0)
                return -1;
@@ -125,8 +136,6 @@ static void update(const char *name, unsigned char *old_sha1, unsigned char *new
        memcpy(lock_name + namelen, ".lock", 6);
 
        strcpy(new_hex, sha1_to_hex(new_sha1));
-       new_hex[40] = '\n';
-       new_hex[41] = 0;
        old_hex = sha1_to_hex(old_sha1);
        if (!has_sha1_file(new_sha1))
                die("unpack should have generated %s, but I can't find it!", new_hex);
@@ -134,7 +143,14 @@ static void update(const char *name, unsigned char *old_sha1, unsigned char *new
        newfd = open(lock_name, O_CREAT | O_EXCL | O_WRONLY, 0644);
        if (newfd < 0)
                die("unable to create %s (%s)", lock_name, strerror(errno));
+
+       /* Write the ref with an ending '\n' */
+       new_hex[40] = '\n';
+       new_hex[41] = 0;
        written = write(newfd, new_hex, 41);
+       /* Remove the '\n' again */
+       new_hex[40] = 0;
+
        close(newfd);
        if (written != 41) {
                unlink(lock_name);