[PATCH] GIT: Create tar archives of tree on the fly

Write commit ID to global extended pax header at the beginning of the tar
file, if possible.  get-tar-commit-id.c is an example program to get the
ID back out of such a tar archive.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

get-tar-commit-id.c

@@ -0,0 +1,27 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#define HEADERSIZE	1024
+
+int main(int argc, char **argv)
+{
+	char buffer[HEADERSIZE];
+	ssize_t n;
+
+	n = read(0, buffer, HEADERSIZE);
+	if (n < HEADERSIZE) {
+		fprintf(stderr, "read error\n");
+		return 3;
+	}
+	if (buffer[156] != 'g')
+		return 1;
+	if (memcmp(&buffer[512], "52 comment=", 11))
+		return 1;
+	n = write(1, &buffer[523], 41);
+	if (n < 41) {
+		fprintf(stderr, "write error\n");
+		return 2;
+	}
+	return 0;
+}