Add a "checkout-cache" command which does what the name suggests.

I'll also eventually change "read-tree" to only update the cache
information, instead of doing a checkout of the tree. Much nicer.

Makefile

@@ -1,7 +1,8 @@
 CFLAGS=-g -O3 -Wall
 CC=gcc
 
-PROG=update-cache show-diff init-db write-tree read-tree commit-tree cat-file fsck-cache
+PROG=	update-cache show-diff init-db write-tree read-tree commit-tree \
+	cat-file fsck-cache checkout-cache
 
 all: $(PROG)
 
@@ -33,6 +34,9 @@ cat-file: cat-file.o read-cache.o
 fsck-cache: fsck-cache.o read-cache.o
 	$(CC) $(CFLAGS) -o fsck-cache fsck-cache.o read-cache.o $(LIBS)
 
+checkout-cache: checkout-cache.o read-cache.o
+	$(CC) $(CFLAGS) -o checkout-cache checkout-cache.o read-cache.o $(LIBS)
+
 read-cache.o: cache.h
 show-diff.o: cache.h
 

checkout-cache.c

@@ -0,0 +1,140 @@
+/*
+ * Check-out files from the "current cache directory"
+ *
+ * Copyright (C) 2005 Linus Torvalds
+ *
+ * Careful: order of argument flags does matter. For example,
+ *
+ *	checkout-cache -a -f file.c
+ *
+ * Will first check out all files listed in the cache (but not
+ * overwrite any old ones), and then force-checkout "file.c" a
+ * second time (ie that one _will_ overwrite any old contents
+ * with the same filename).
+ *
+ * Also, just doing "checkout-cache" does nothing. You probably
+ * meant "checkout-cache -a". And if you want to force it, you
+ * want "checkout-cache -f -a".
+ *
+ * Intuitiveness is not the goal here. Repeatability is. The
+ * reason for the "no arguments means no work" thing is that
+ * from scripts you are supposed to be able to do things like
+ *
+ *	find . -name '*.h' -print0 | xargs -0 checkout-cache -f --
+ *
+ * which will force all existing *.h files to be replaced with
+ * their cached copies. If an empty command line implied "all",
+ * then this would force-refresh everything in the cache, which
+ * was not the point.
+ *
+ * Oh, and the "--" is just a good idea when you know the rest
+ * will be filenames. Just so that you wouldn't have a filename
+ * of "-a" causing problems (not possible in the above example,
+ * but get used to it in scripting!).
+ */
+#include "cache.h"
+
+static int force = 0, quiet = 0;
+
+static int write_entry(struct cache_entry *ce)
+{
+	int fd;
+	void *new;
+	unsigned long size;
+	long wrote;
+
+	new = read_sha1_file(ce->sha1, "blob", &size);
+	if (!new) {
+		fprintf(stderr, "checkout-cache: unable to read sha1 file of %s (%s)",
+			ce->name, sha1_to_hex(ce->sha1));
+		return -1;
+	}
+	fd = open(ce->name, O_WRONLY | O_CREAT | O_TRUNC, 0600);
+	if (fd < 0) {
+		fprintf(stderr, "checkout-cache: unable to create %s (%s)",
+			ce->name, strerror(errno));
+		free(new);
+		return -1;
+	}
+	wrote = write(fd, new, size);
+	close(fd);
+	free(new);
+	if (wrote == size)
+		return 0;
+	fprintf(stderr, "checkout-cache: unable to write %s", ce->name);
+	return -1;
+}
+
+static int checkout_entry(struct cache_entry *ce)
+{
+	if (!force) {
+		struct stat st;
+
+		if (!stat(ce->name, &st)) {
+			unsigned changed = cache_match_stat(ce, &st);
+			if (!changed)
+				return 0;
+			if (!quiet)
+				fprintf(stderr, "checkout-cache: %s already exists", ce->name);
+			return -1;
+		}
+	}
+	return write_entry(ce);
+}
+
+static int checkout_file(const char *name)
+{
+	int pos = cache_name_pos(name, strlen(name));
+	if (pos < 0) {
+		if (!quiet)
+			fprintf(stderr, "checkout-cache: %s is not in the cache", name);
+		return -1;
+	}
+	return checkout_entry(active_cache[pos]);
+}
+
+static int checkout_all(void)
+{
+	int i;
+
+	for (i = 0; i < active_nr ; i++) {
+		struct cache_entry *ce = active_cache[i];
+		if (checkout_entry(ce) < 0)
+			return -1;
+	}
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	int i, force_filename = 0;
+
+	if (read_cache() < 0) {
+		fprintf(stderr, "Invalid cache");
+		exit(1);
+	}
+
+	for (i = 1; i < argc; i++) {
+		const char *arg = argv[i];
+		if (!force_filename) {
+			if (!strcmp(arg, "-a")) {
+				checkout_all();
+				continue;
+			}
+			if (!strcmp(arg, "--")) {
+				force_filename = 1;
+				continue;
+			}
+			if (!strcmp(arg, "-f")) {
+				force = 1;
+				continue;
+			}
+			if (!strcmp(arg, "-q")) {
+				quiet = 1;
+				continue;
+			}
+		}
+		checkout_file(arg);
+	}
+	return 0;
+}