pack-objects --unpacked=<existing pack> option.

Incremental repack without -a essentially boils down to:

	rev-list --objects --unpacked --all |
        pack-objects $new_pack

which picks up all loose objects that are still live and creates
a new pack.

This implements --unpacked=<existing pack> option to tell the
revision walking machinery to pretend as if objects in such a
pack are unpacked for the purpose of object listing.  With this,
we could say:

	rev-list --objects --unpacked=$active_pack --all |
	pack-objects $new_pack

instead, to mean "all live loose objects but pretend as if
objects that are in this pack are also unpacked".  The newly
created pack would be perfect for updating $active_pack by
replacing it.

Since pack-objects now knows how to do the rev-list's work
itself internally, you can also write the above example by:

	pack-objects --unpacked=$active_pack --all $new_pack </dev/null

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-count-objects.c

@@ -62,7 +62,7 @@ static void count_objects(DIR *d, char *path, int len, int verbose,
 		hex[40] = 0;
 		if (get_sha1_hex(hex, sha1))
 			die("internal error");
-		if (has_sha1_pack(sha1))
+		if (has_sha1_pack(sha1, NULL))
 			(*packed_loose)++;
 	}
 }

builtin-prune-packed.c

@@ -19,7 +19,7 @@ static void prune_dir(int i, DIR *dir, char *pathname, int len)
 		memcpy(hex+2, de->d_name, 38);
 		if (get_sha1_hex(hex, sha1))
 			continue;
-		if (!has_sha1_pack(sha1))
+		if (!has_sha1_pack(sha1, NULL))
 			continue;
 		memcpy(pathname + len, de->d_name, 38);
 		if (dryrun)

cache.h

@@ -259,7 +259,7 @@ extern int write_sha1_from_fd(const unsigned char *sha1, int fd, char *buffer,
 extern int write_sha1_to_fd(int fd, const unsigned char *sha1);
 extern int move_temp_to_file(const char *tmpfile, const char *filename);
 
-extern int has_sha1_pack(const unsigned char *sha1);
+extern int has_sha1_pack(const unsigned char *sha1, const char **ignore);
 extern int has_sha1_file(const unsigned char *sha1);
 extern void *map_sha1_file(const unsigned char *sha1, unsigned long *);
 extern int legacy_loose_object(unsigned char *);

revision.c

@@ -416,7 +416,8 @@ static void limit_list(struct rev_info *revs)
 
 		if (revs->max_age != -1 && (commit->date < revs->max_age))
 			obj->flags |= UNINTERESTING;
-		if (revs->unpacked && has_sha1_pack(obj->sha1))
+		if (revs->unpacked &&
+		    has_sha1_pack(obj->sha1, revs->ignore_packed))
 			obj->flags |= UNINTERESTING;
 		add_parents_to_list(revs, commit, &list);
 		if (obj->flags & UNINTERESTING) {
@@ -671,6 +672,16 @@ int handle_revision_arg(const char *arg, struct rev_info *revs,
 	return 0;
 }
 
+static void add_ignore_packed(struct rev_info *revs, const char *name)
+{
+	int num = ++revs->num_ignore_packed;
+
+	revs->ignore_packed = xrealloc(revs->ignore_packed,
+				       sizeof(const char **) * (num + 1));
+	revs->ignore_packed[num-1] = name;
+	revs->ignore_packed[num] = NULL;
+}
+
 /*
  * Parse revision information, filling in the "rev_info" structure,
  * and removing the used arguments from the argument list.
@@ -811,6 +822,14 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, const ch
 			}
 			if (!strcmp(arg, "--unpacked")) {
 				revs->unpacked = 1;
+				free(revs->ignore_packed);
+				revs->ignore_packed = NULL;
+				revs->num_ignore_packed = 0;
+				continue;
+			}
+			if (!strncmp(arg, "--unpacked=", 11)) {
+				revs->unpacked = 1;
+				add_ignore_packed(revs, arg+11);
 				continue;
 			}
 			if (!strcmp(arg, "-r")) {
@@ -1057,7 +1076,8 @@ struct commit *get_revision(struct rev_info *revs)
 		 */
 		if (!revs->limited) {
 			if ((revs->unpacked &&
-			     has_sha1_pack(commit->object.sha1)) ||
+			     has_sha1_pack(commit->object.sha1,
+					   revs->ignore_packed)) ||
 			    (revs->max_age != -1 &&
 			     (commit->date < revs->max_age)))
 				continue;

revision.h

@@ -38,7 +38,7 @@ struct rev_info {
 			blob_objects:1,
 			edge_hint:1,
 			limited:1,
-			unpacked:1,
+			unpacked:1, /* see also ignore_packed below */
 			boundary:1,
 			parents:1;
 
@@ -57,6 +57,10 @@ struct rev_info {
 	unsigned int	shown_one:1,
 			abbrev_commit:1,
 			relative_date:1;
+
+	const char **ignore_packed; /* pretend objects in these are unpacked */
+	int num_ignore_packed;
+
 	unsigned int	abbrev;
 	enum cmit_fmt	commit_format;
 	struct log_info *loginfo;

sha1_file.c

@@ -1189,12 +1189,20 @@ int find_pack_entry_one(const unsigned char *sha1,
 	return 0;
 }
 
-static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
+static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e, const char **ignore_packed)
 {
 	struct packed_git *p;
 	prepare_packed_git();
 
 	for (p = packed_git; p; p = p->next) {
+		if (ignore_packed) {
+			const char **ig;
+			for (ig = ignore_packed; *ig; ig++)
+				if (!strcmp(p->pack_name, *ig))
+					break;
+			if (*ig)
+				continue;
+		}
 		if (find_pack_entry_one(sha1, e, p))
 			return 1;
 	}
@@ -1227,10 +1235,10 @@ int sha1_object_info(const unsigned char *sha1, char *type, unsigned long *sizep
 	if (!map) {
 		struct pack_entry e;
 
-		if (find_pack_entry(sha1, &e))
+		if (find_pack_entry(sha1, &e, NULL))
 			return packed_object_info(&e, type, sizep);
 		reprepare_packed_git();
-		if (find_pack_entry(sha1, &e))
+		if (find_pack_entry(sha1, &e, NULL))
 			return packed_object_info(&e, type, sizep);
 		return error("unable to find %s", sha1_to_hex(sha1));
 	}
@@ -1253,7 +1261,7 @@ static void *read_packed_sha1(const unsigned char *sha1, char *type, unsigned lo
 {
 	struct pack_entry e;
 
-	if (!find_pack_entry(sha1, &e)) {
+	if (!find_pack_entry(sha1, &e, NULL)) {
 		error("cannot read sha1_file for %s", sha1_to_hex(sha1));
 		return NULL;
 	}
@@ -1266,7 +1274,7 @@ void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size
 	void *map, *buf;
 	struct pack_entry e;
 
-	if (find_pack_entry(sha1, &e))
+	if (find_pack_entry(sha1, &e, NULL))
 		return read_packed_sha1(sha1, type, size);
 	map = map_sha1_file(sha1, &mapsize);
 	if (map) {
@@ -1275,7 +1283,7 @@ void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size
 		return buf;
 	}
 	reprepare_packed_git();
-	if (find_pack_entry(sha1, &e))
+	if (find_pack_entry(sha1, &e, NULL))
 		return read_packed_sha1(sha1, type, size);
 	return NULL;
 }
@@ -1707,10 +1715,10 @@ int has_pack_file(const unsigned char *sha1)
 	return 1;
 }
 
-int has_sha1_pack(const unsigned char *sha1)
+int has_sha1_pack(const unsigned char *sha1, const char **ignore_packed)
 {
 	struct pack_entry e;
-	return find_pack_entry(sha1, &e);
+	return find_pack_entry(sha1, &e, ignore_packed);
 }
 
 int has_sha1_file(const unsigned char *sha1)
@@ -1718,7 +1726,7 @@ int has_sha1_file(const unsigned char *sha1)
 	struct stat st;
 	struct pack_entry e;
 
-	if (find_pack_entry(sha1, &e))
+	if (find_pack_entry(sha1, &e, NULL))
 		return 1;
 	return find_sha1_file(sha1, &st) ? 1 : 0;
 }