Add a "git-daemon" that listens on a TCP port

.. and does a "git-upload-pack" on demand.

Makefile

@@ -48,7 +48,7 @@ PROG=   git-update-cache git-diff-files git-init-db git-write-tree \
 	git-diff-stages git-rev-parse git-patch-id git-pack-objects \
 	git-unpack-objects git-verify-pack git-receive-pack git-send-pack \
 	git-prune-packed git-fetch-pack git-upload-pack git-clone-pack \
-	git-show-index
+	git-show-index git-daemon
 
 all: $(PROG)
 

daemon.c

@@ -0,0 +1,117 @@
+#include "cache.h"
+#include "pkt-line.h"
+#include <sys/socket.h>
+#include <netinet/in.h>
+
+static const char daemon_usage[] = "git-daemon [--port=n]";
+
+static int upload(char *dir, int dirlen)
+{
+	if (chdir(dir) < 0)
+		return -1;
+	chdir(".git");
+
+	/*
+	 * Security on the cheap.
+	 *
+	 * We want a readable HEAD, usable "objects" directory, and 
+	 * a "git-daemon-export-ok" flag that says that the other side
+	 * is ok with us doing this.
+	 */
+	if (access("git-daemon-export-ok", F_OK) ||
+	    access("objects/00", X_OK) ||
+	    access("HEAD", R_OK))
+		return -1;
+
+	/* git-upload-pack only ever reads stuff, so this is safe */
+	execlp("git-upload-pack", "git-upload-pack", ".", NULL);
+	return -1;
+}
+
+static int execute(char *line, int len)
+{
+	if (!strncmp("git-upload-pack /", line, 17))
+		return upload(line + 16, len - 16);
+
+	fprintf(stderr, "got bad connection '%s'\n", line);
+	return -1;
+}
+
+static void handle(int incoming, struct sockaddr_in *addr, int addrlen)
+{
+	static char line[1000];
+	int len;
+
+	if (fork()) {
+		close(incoming);
+		return;
+	}
+
+	dup2(incoming, 0);
+	dup2(incoming, 1);
+	close(incoming);
+	len = packet_read_line(0, line, sizeof(line));
+
+	if (len && line[len-1] == '\n')
+		line[--len] = 0;
+
+	exit(execute(line, len));
+}
+
+static int serve(int port)
+{
+	int sockfd;
+	struct sockaddr_in addr;
+
+	sockfd = socket(PF_INET, SOCK_STREAM, IPPROTO_IP);
+	if (sockfd < 0)
+		die("unable to open socket (%s)", strerror(errno));
+	memset(&addr, 0, sizeof(addr));
+	addr.sin_port = htons(port);
+	addr.sin_family = AF_INET;
+	if (bind(sockfd, (void *)&addr, sizeof(addr)) < 0)
+		die("unable to bind to port %d (%s)", port, strerror(errno));
+	if (listen(sockfd, 5) < 0)
+		die("unable to listen to port %d (%s)", port, strerror(errno));
+
+	for (;;) {
+		struct sockaddr_in in;
+		socklen_t addrlen = sizeof(in);
+		int incoming = accept(sockfd, (void *)&in, &addrlen);
+
+		if (incoming < 0) {
+			switch (errno) {
+			case EAGAIN:
+			case EINTR:
+			case ECONNABORTED:
+				continue;
+			default:
+				die("accept returned %s", strerror(errno));
+			}
+		}
+		handle(incoming, &in, addrlen);
+	}
+}
+
+int main(int argc, char **argv)
+{
+	int port = DEFAULT_GIT_PORT;
+	int i;
+
+	for (i = 1; i < argc; i++) {
+		char *arg = argv[i];
+
+		if (!strncmp(arg, "--port=", 7)) {
+			char *end;
+			unsigned long n;
+			n = strtoul(arg+7, &end, 0);
+			if (arg[7] && !*end) {
+				port = n;
+				continue;
+			}
+		}
+		usage(daemon_usage);
+	}
+
+	return serve(port);
+}