[PATCH] Add update-server-info.

The git-update-server-info command prepares informational files
to help clients discover the contents of a repository, and pull
from it via a dumb transport protocols.  Currently, the
following files are produced.

 - The $repo/info/refs file lists the name of heads and tags
   available in the $repo/refs/ directory, along with their
   SHA1.  This can be used by git-ls-remote command running on
   the client side.

 - The $repo/info/rev-cache file describes the commit ancestry
   reachable from references in the $repo/refs/ directory.  This
   file is in an append-only binary format to make the server
   side friendly to rsync mirroring scheme, and can be read by
   git-show-rev-cache command.

 - The $repo/objects/info/pack file lists the name of the packs
   available, the interdependencies among them, and the head
   commits and tags contained in them.  Along with the other two
   files, this is designed to help clients to make smart pull
   decisions.

The git-receive-pack command is changed to invoke it at the end,
so just after a push to a public repository finishes via "git
push", the server info is automatically updated.

In addition, building of the rev-cache file can be done by a
standalone git-build-rev-cache command separately.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Makefile

@@ -50,7 +50,8 @@ 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-daemon git-var git-peek-remote
+	git-show-index git-daemon git-var git-peek-remote \
+	git-update-server-info git-show-rev-cache git-build-rev-cache
 
 all: $(PROG)
 
@@ -65,6 +66,9 @@ LIB_FILE=libgit.a
 LIB_H=cache.h object.h blob.h tree.h commit.h tag.h delta.h epoch.h csum-file.h \
 	pack.h pkt-line.h refs.h
 
+LIB_H += rev-cache.h
+LIB_OBJS += rev-cache.o
+
 LIB_H += strbuf.h
 LIB_OBJS += strbuf.o
 
@@ -76,6 +80,7 @@ LIB_OBJS += diff.o diffcore-rename.o diffcore-pickaxe.o diffcore-pathspec.o \
 	count-delta.o diffcore-break.o diffcore-order.o
 
 LIB_OBJS += gitenv.o
+LIB_OBJS += server-info.o
 
 LIBS = $(LIB_FILE)
 LIBS += -lz
@@ -152,6 +157,9 @@ git-prune-packed: prune-packed.c
 git-fetch-pack: fetch-pack.c
 git-var: var.c
 git-peek-remote: peek-remote.c
+git-update-server-info: update-server-info.c
+git-build-rev-cache: build-rev-cache.c
+git-show-rev-cache: show-rev-cache.c
 
 git-http-pull: LIBS += -lcurl
 git-rev-list: LIBS += -lssl
@@ -165,6 +173,7 @@ object.o: $(LIB_H)
 read-cache.o: $(LIB_H)
 sha1_file.o: $(LIB_H)
 usage.o: $(LIB_H)
+rev-cache.o: $(LIB_H)
 strbuf.o: $(LIB_H)
 gitenv.o: $(LIB_H)
 entry.o: $(LIB_H)

build-rev-cache.c

@@ -0,0 +1,56 @@
+#include "refs.h"
+#include "cache.h"
+#include "commit.h"
+#include "rev-cache.h"
+
+static void process_head_list(int verbose)
+{
+	char buf[512];
+
+	while (fgets(buf, sizeof(buf), stdin)) {
+		unsigned char sha1[20];
+		struct commit *commit;
+
+		if (get_sha1_hex(buf, sha1)) {
+			error("ignoring: %s", buf);
+			continue;
+		}
+		if (!(commit = lookup_commit_reference(sha1))) {
+			error("not a commit: %s", sha1_to_hex(sha1));
+			continue;
+		}
+		record_rev_cache(commit->object.sha1, verbose ? stderr : NULL);
+	}
+}
+
+
+static const char *build_rev_cache_usage =
+"git-build-rev-cache <rev-cache-file> < list-of-heads";
+
+int main(int ac, char **av)
+{
+	int verbose = 0;
+	const char *path;
+
+	while (1 < ac && av[1][0] == '-') {
+		if (!strcmp(av[1], "-v"))
+			verbose = 1;
+		else
+			usage(build_rev_cache_usage);
+		ac--; av++;
+	}
+
+	if (ac != 2)
+		usage(build_rev_cache_usage);
+
+	path = av[1];
+
+	/* read existing rev-cache */
+	read_rev_cache(path, NULL, 0);
+
+	process_head_list(verbose);
+
+	/* update the rev-cache database by appending newly found one to it */
+	write_rev_cache(path, path);
+	return 0;
+}

cache.h

@@ -308,4 +308,7 @@ extern int find_pack_entry_one(const unsigned char *, struct pack_entry *, struc
 extern void *unpack_entry_gently(struct pack_entry *, char *, unsigned long *);
 extern void packed_object_info_detail(struct pack_entry *, char *, unsigned long *, unsigned long *, int *, unsigned char *);
 
+/* Dumb servers support */
+extern int update_server_info(int);
+
 #endif /* CACHE_H */

receive-pack.c

@@ -110,6 +110,7 @@ static void execute_commands(void)
 		update(cmd->ref_name, cmd->old_sha1, cmd->new_sha1);
 		cmd = cmd->next;
 	}
+	update_server_info(0);
 }
 
 static void read_head_info(void)