Make git-write-tree a builtin

Signed-off-by: Lukas Sandström <lukass@etek.chalmers.se>
Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-write-tree.c

@@ -0,0 +1,88 @@
+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) Linus Torvalds, 2005
+ */
+#include "builtin.h"
+#include "cache.h"
+#include "tree.h"
+#include "cache-tree.h"
+
+static const char write_tree_usage[] =
+"git-write-tree [--missing-ok] [--prefix=<prefix>/]";
+
+int write_tree(unsigned char *sha1, int missing_ok, const char *prefix)
+{
+	int entries, was_valid, newfd;
+
+	/* We can't free this memory, it becomes part of a linked list parsed atexit() */
+	struct lock_file *lock_file = xmalloc(sizeof(struct lock_file));
+
+	newfd = hold_lock_file_for_update(lock_file, get_index_file());
+
+	entries = read_cache();
+	if (entries < 0)
+		die("git-write-tree: error reading cache");
+
+	if (!active_cache_tree)
+		active_cache_tree = cache_tree();
+
+	was_valid = cache_tree_fully_valid(active_cache_tree);
+
+	if (!was_valid) {
+		if (cache_tree_update(active_cache_tree,
+				      active_cache, active_nr,
+				      missing_ok, 0) < 0)
+			die("git-write-tree: error building trees");
+		if (0 <= newfd) {
+			if (!write_cache(newfd, active_cache, active_nr))
+				commit_lock_file(lock_file);
+		}
+		/* Not being able to write is fine -- we are only interested
+		 * in updating the cache-tree part, and if the next caller
+		 * ends up using the old index with unupdated cache-tree part
+		 * it misses the work we did here, but that is just a
+		 * performance penalty and not a big deal.
+		 */
+	}
+
+	if (prefix) {
+		struct cache_tree *subtree =
+			cache_tree_find(active_cache_tree, prefix);
+		memcpy(sha1, subtree->sha1, 20);
+	}
+	else
+		memcpy(sha1, active_cache_tree->sha1, 20);
+
+	rollback_lock_file(lock_file);
+
+	return 0;
+}
+
+int cmd_write_tree(int argc, const char **argv, char **envp)
+{
+	int missing_ok = 0, ret;
+	const char *prefix = NULL;
+	unsigned char sha1[20];
+
+	setup_git_directory();
+
+	while (1 < argc) {
+		const char *arg = argv[1];
+		if (!strcmp(arg, "--missing-ok"))
+			missing_ok = 1;
+		else if (!strncmp(arg, "--prefix=", 9))
+			prefix = arg + 9;
+		else
+			die(write_tree_usage);
+		argc--; argv++;
+	}
+
+	if (argc > 2)
+		die("too many options");
+
+	ret = write_tree(sha1, missing_ok, prefix);
+	printf("%s\n", sha1_to_hex(sha1));
+
+	return ret;
+}