Implemented branch handling and basic tree support in fast-import.

This provides the basic data structures needed to store trees in
memory while we are processing them for a branch.  What we are
attempting to do is track one complete tree for each branch that
the frontend has registered with us through the 'newb' (new_branch)
command.  When the frontend edits that tree through 'updf' or 'delf'
commands we'll mark the affected tree(s) as being dirty and recompute
their objects during 'comt' (commit).

Currently the protocol is decidedly _not_ user friendly.  I crashed
fast-import by giving it bad input data from Perl.  I may try to
improve upon it, or at least upon its error handling.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

fast-import.c

@@ -24,14 +24,39 @@ struct object_entry_block
 struct last_object
 {
 	void *data;
-	unsigned long len;
-	int depth;
+	unsigned int len;
+	unsigned int depth;
 	unsigned char sha1[20];
 };
 
+struct tree;
+struct tree_entry
+{
+	struct tree *tree;
+	mode_t mode;
+	unsigned char sha1[20];
+	char name[FLEX_ARRAY]; /* more */
+};
+
+struct tree
+{
+	struct last_object last_tree;
+	unsigned long entry_count;
+	struct tree_entry **entries;
+};
+
+struct branch
+{
+	struct branch *next_branch;
+	struct tree_entry tree;
+	unsigned char sha1[20];
+	const char *name;
+};
+
 /* Stats and misc. counters. */
 static int max_depth = 10;
 static unsigned long alloc_count;
+static unsigned long branch_count;
 static unsigned long object_count;
 static unsigned long duplicate_count;
 static unsigned long object_count_by_type[9];
@@ -49,6 +74,10 @@ struct object_entry *object_table[1 << 16];
 /* Our last blob */
 struct last_object last_blob;
 
+/* Branch data */
+struct branch *branches;
+struct branch *current_branch;
+
 static void alloc_objects(int cnt)
 {
 	struct object_entry_block *b;
@@ -129,6 +158,32 @@ static ssize_t ywrite(int fd, void *buffer, size_t length)
 	return ret;
 }
 
+static const char* read_string()
+{
+	static char sn[PATH_MAX];
+	unsigned long slen;
+
+	if (yread(0, &slen, 4) != 4)
+		die("Can't obtain string");
+	if (!slen)
+		return 0;
+	if (slen > (PATH_MAX - 1))
+		die("Can't handle excessive string length %lu", slen);
+
+	if (yread(0, sn, slen) != slen)
+		die("Can't obtain string of length %lu", slen);
+	sn[slen] = 0;
+	return sn;
+}
+
+static const char* read_required_string()
+{
+	const char *r = read_string();
+	if (!r)
+		die("Expected string command parameter, didn't find one");
+	return r;
+}
+
 static unsigned long encode_header(
 	enum object_type type,
 	unsigned long size,
@@ -156,7 +211,8 @@ static int store_object(
 	enum object_type type,
 	void *dat,
 	unsigned long datlen,
-	struct last_object *last)
+	struct last_object *last,
+	unsigned char *sha1out)
 {
 	void *out, *delta;
 	struct object_entry *e;
@@ -171,6 +227,8 @@ static int store_object(
 	SHA1_Update(&c, hdr, hdrlen);
 	SHA1_Update(&c, dat, datlen);
 	SHA1_Final(sha1, &c);
+	if (sha1out)
+		memcpy(sha1out, sha1, sizeof(sha1));
 
 	e = insert_object(sha1);
 	if (e->offset) {
@@ -347,10 +405,108 @@ static void new_blob()
 	if (yread(0, dat, datlen) != datlen)
 		die("Con't obtain %lu bytes of blob data", datlen);
 
-	if (!store_object(OBJ_BLOB, dat, datlen, &last_blob))
+	if (!store_object(OBJ_BLOB, dat, datlen, &last_blob, 0))
 		free(dat);
 }
 
+static struct branch* lookup_branch(const char *name)
+{
+	struct branch *b;
+	for (b = branches; b; b = b->next_branch) {
+		if (!strcmp(name, b->name))
+			return b;
+	}
+	die("No branch named '%s' has been declared", name);
+}
+
+static struct tree* deep_copy_tree (struct tree *t)
+{
+	struct tree *r = xmalloc(sizeof(struct tree));
+	unsigned long i;
+
+	if (t->last_tree.data) {
+		r->last_tree.data = xmalloc(t->last_tree.len);
+		r->last_tree.len = t->last_tree.len;
+		r->last_tree.depth = t->last_tree.depth;
+		memcpy(r->last_tree.data, t->last_tree.data, t->last_tree.len);
+		memcpy(r->last_tree.sha1, t->last_tree.sha1, sizeof(t->last_tree.sha1));
+	}
+
+	r->entry_count = t->entry_count;
+	r->entries = xmalloc(t->entry_count * sizeof(struct tree_entry*));
+	for (i = 0; i < t->entry_count; i++) {
+		struct tree_entry *a = t->entries[i];
+		struct tree_entry *b;
+
+		b = xmalloc(sizeof(struct tree_entry) + strlen(a->name) + 1);
+		b->tree = a->tree ? deep_copy_tree(a->tree) : 0;
+		b->mode = a->mode;
+		memcpy(b->sha1, a->sha1, sizeof(a->sha1));
+		strcpy(b->name, a->name);
+		r->entries[i] = b;
+	}
+
+	return r;
+}
+
+static void store_tree (struct tree_entry *e)
+{
+	struct tree *t = e->tree;
+	unsigned long maxlen, i;
+	char *buf, *c;
+
+	if (memcmp(null_sha1, e->sha1, sizeof(e->sha1)))
+		return;
+
+	maxlen = t->entry_count * 32;
+	for (i = 0; i < t->entry_count; i++)
+		maxlen += strlen(t->entries[i]->name);
+
+	buf = c = xmalloc(maxlen);
+	for (i = 0; i < t->entry_count; i++) {
+		struct tree_entry *e = t->entries[i];
+		c += sprintf(c, "%o %s", e->mode, e->name) + 1;
+		if (e->tree)
+			store_tree(e);
+		memcpy(c, e->sha1, sizeof(e->sha1));
+		c += sizeof(e->sha1);
+	}
+
+	if (!store_object(OBJ_TREE, buf, c - buf, &t->last_tree, e->sha1))
+		free(buf);
+}
+
+static void new_branch()
+{
+	struct branch *nb = xcalloc(1, sizeof(struct branch));
+	const char *source_name;
+
+	nb->name = strdup(read_required_string());
+	source_name = read_string();
+	if (source_name) {
+		struct branch *sb = lookup_branch(source_name);
+		nb->tree.tree = deep_copy_tree(sb->tree.tree);
+		memcpy(nb->tree.sha1, sb->tree.sha1, sizeof(sb->tree.sha1));
+		memcpy(nb->sha1, sb->sha1, sizeof(sb->sha1));
+	} else {
+		nb->tree.tree = xcalloc(1, sizeof(struct tree));
+		nb->tree.tree->entries = xmalloc(8*sizeof(struct tree_entry*));
+	}
+	nb->next_branch = branches;
+	branches = nb;
+	branch_count++;
+}
+
+static void set_branch()
+{
+	current_branch = lookup_branch(read_required_string());
+}
+
+static void commit()
+{
+	store_tree(&current_branch->tree);
+}
+
 int main(int argc, const char **argv)
 {
 	const char *base_name = argv[1];
@@ -376,7 +532,10 @@ int main(int argc, const char **argv)
 			break;
 
 		switch (cmd) {
-		case 'blob': new_blob(); break;
+		case 'blob': new_blob();   break;
+		case 'newb': new_branch(); break;
+		case 'setb': set_branch(); break;
+		case 'comt': commit();     break;
 		default:
 			die("Invalid command %lu", cmd);
 		}
@@ -393,6 +552,7 @@ int main(int argc, const char **argv)
 	fprintf(stderr, "      trees  :   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_TREE], duplicate_count_by_type[OBJ_TREE]);
 	fprintf(stderr, "      commits:   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_COMMIT], duplicate_count_by_type[OBJ_COMMIT]);
 	fprintf(stderr, "      tags   :   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_TAG], duplicate_count_by_type[OBJ_TAG]);
+	fprintf(stderr, "Total branches:  %10lu\n", branch_count);
 	fprintf(stderr, "---------------------------------------------------\n");
 
 	stat(pack_name, &sb);