Make fiel checkout function available to the git library

The merge stuff will want it soon, and we don't want to
duplicate all the work..

entry.c

@@ -0,0 +1,160 @@
+#include <sys/types.h>
+#include <dirent.h>
+#include "cache.h"
+
+static void create_directories(const char *path, struct checkout *state)
+{
+	int len = strlen(path);
+	char *buf = xmalloc(len + 1);
+	const char *slash = path;
+
+	while ((slash = strchr(slash+1, '/')) != NULL) {
+		len = slash - path;
+		memcpy(buf, path, len);
+		buf[len] = 0;
+		if (mkdir(buf, 0755)) {
+			if (errno == EEXIST) {
+				struct stat st;
+				if (len > state->base_dir_len && state->force && !unlink(buf) && !mkdir(buf, 0755))
+					continue;
+				if (!stat(buf, &st) && S_ISDIR(st.st_mode))
+					continue; /* ok */
+			}
+			die("cannot create directory at %s", buf);
+		}
+	}
+	free(buf);
+}
+
+static void remove_subtree(const char *path)
+{
+	DIR *dir = opendir(path);
+	struct dirent *de;
+	char pathbuf[PATH_MAX];
+	char *name;
+	
+	if (!dir)
+		die("cannot opendir %s", path);
+	strcpy(pathbuf, path);
+	name = pathbuf + strlen(path);
+	*name++ = '/';
+	while ((de = readdir(dir)) != NULL) {
+		struct stat st;
+		if ((de->d_name[0] == '.') &&
+		    ((de->d_name[1] == 0) ||
+		     ((de->d_name[1] == '.') && de->d_name[2] == 0)))
+			continue;
+		strcpy(name, de->d_name);
+		if (lstat(pathbuf, &st))
+			die("cannot lstat %s", pathbuf);
+		if (S_ISDIR(st.st_mode))
+			remove_subtree(pathbuf);
+		else if (unlink(pathbuf))
+			die("cannot unlink %s", pathbuf);
+	}
+	closedir(dir);
+	if (rmdir(path))
+		die("cannot rmdir %s", path);
+}
+
+static int create_file(const char *path, unsigned int mode, int force)
+{
+	int fd;
+
+	mode = (mode & 0100) ? 0777 : 0666;
+	fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, mode);
+	if (fd < 0) {
+		if (errno == EISDIR && force) {
+			remove_subtree(path);
+			fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, mode);
+		}
+	}
+	return fd;
+}
+
+static int write_entry(struct cache_entry *ce, const char *path, struct checkout *state)
+{
+	int fd;
+	void *new;
+	unsigned long size;
+	long wrote;
+	char type[20];
+	char target[1024];
+
+	new = read_sha1_file(ce->sha1, type, &size);
+	if (!new || strcmp(type, "blob")) {
+		if (new)
+			free(new);
+		return error("git-checkout-cache: unable to read sha1 file of %s (%s)",
+			path, sha1_to_hex(ce->sha1));
+	}
+	switch (ntohl(ce->ce_mode) & S_IFMT) {
+	case S_IFREG:
+		fd = create_file(path, ntohl(ce->ce_mode), state->force);
+		if (fd < 0) {
+			free(new);
+			return error("git-checkout-cache: unable to create file %s (%s)",
+				path, strerror(errno));
+		}
+		wrote = write(fd, new, size);
+		close(fd);
+		free(new);
+		if (wrote != size)
+			return error("git-checkout-cache: unable to write file %s", path);
+		break;
+	case S_IFLNK:
+		memcpy(target, new, size);
+		target[size] = '\0';
+		if (symlink(target, path)) {
+			free(new);
+			return error("git-checkout-cache: unable to create symlink %s (%s)",
+				path, strerror(errno));
+		}
+		free(new);
+		break;
+	default:
+		free(new);
+		return error("git-checkout-cache: unknown file mode for %s", path);
+	}
+
+	if (state->update) {
+		struct stat st;
+		lstat(ce->name, &st);
+		fill_stat_cache_info(ce, &st);
+	}
+	return 0;
+}
+
+int checkout_entry(struct cache_entry *ce, struct checkout *state)
+{
+	struct stat st;
+	static char path[MAXPATHLEN+1];
+	int len = state->base_dir_len;
+
+	memcpy(path, state->base_dir, len);
+	strcpy(path + len, ce->name);
+
+	if (!lstat(path, &st)) {
+		unsigned changed = ce_match_stat(ce, &st);
+		if (!changed)
+			return 0;
+		if (!state->force) {
+			if (!state->quiet)
+				fprintf(stderr, "git-checkout-cache: %s already exists\n", path);
+			return 0;
+		}
+
+		/*
+		 * We unlink the old file, to get the new one with the
+		 * right permissions (including umask, which is nasty
+		 * to emulate by hand - much easier to let the system
+		 * just do the right thing)
+		 */
+		unlink(path);
+	} else if (state->not_new) 
+		return 0;
+	create_directories(path, state);
+	return write_entry(ce, path, state);
+}
+
+