Git の最初のコミットを読む

git clone https://github.com/git/git.git
cd git
git rev-list --max-parents=0 HEAD

$ tree
.
├── cache.h
├── cat-file.c
├── commit-tree.c
├── init-db.c
├── Makefile
├── read-cache.c
├── read-tree.c
├── README
├── show-diff.c
├── update-cache.c
└── write-tree.c

1 directory, 11 files

#include "cache.h"

int main(int argc, char **argv)
{
	char *sha1_dir = getenv(DB_ENVIRONMENT), *path;
	int len, i, fd;

	if (mkdir(".dircache", 0700) < 0) {
		perror("unable to create .dircache");
		exit(1);
	}

	/*
	 * If you want to, you can share the DB area with any number of branches.
	 * That has advantages: you can save space by sharing all the SHA1 objects.
	 * On the other hand, it might just make lookup slower and messier. You
	 * be the judge.
	 */
	sha1_dir = getenv(DB_ENVIRONMENT);
	if (sha1_dir) {
		struct stat st;
		if (!stat(sha1_dir, &st) < 0 && S_ISDIR(st.st_mode))
			return;
		fprintf(stderr, "DB_ENVIRONMENT set to bad directory %s: ", sha1_dir);
	}

	/*
	 * The default case is to have a DB per managed directory. 
	 */
	sha1_dir = DEFAULT_DB_ENVIRONMENT;
	fprintf(stderr, "defaulting to private storage area\n");
	len = strlen(sha1_dir);
	if (mkdir(sha1_dir, 0700) < 0) {
		if (errno != EEXIST) {
			perror(sha1_dir);
			exit(1);
		}
	}
	path = malloc(len + 40);
	memcpy(path, sha1_dir, len);
	for (i = 0; i < 256; i++) {
		sprintf(path+len, "/%02x", i);
		if (mkdir(path, 0700) < 0) {
			if (errno != EEXIST) {
				perror(path);
				exit(1);
			}
		}
	}
	return 0;
}

#define DB_ENVIRONMENT "SHA1_FILE_DIRECTORY"
#define DEFAULT_DB_ENVIRONMENT ".dircache/objects"

#include "cache.h"

static int cache_name_compare(const char *name1, int len1, const char *name2, int len2)
{
	int len = len1 < len2 ? len1 : len2;
	int cmp;

	cmp = memcmp(name1, name2, len);
	if (cmp)
		return cmp;
	if (len1 < len2)
		return -1;
	if (len1 > len2)
		return 1;
	return 0;
}

static int cache_name_pos(const char *name, int namelen)
{
	int first, last;

	first = 0;
	last = active_nr;
	while (last > first) {
		int next = (last + first) >> 1;
		struct cache_entry *ce = active_cache[next];
		int cmp = cache_name_compare(name, namelen, ce->name, ce->namelen);
		if (!cmp)
			return -next-1;
		if (cmp < 0) {
			last = next;
			continue;
		}
		first = next+1;
	}
	return first;
}

static int remove_file_from_cache(char *path)
{
	int pos = cache_name_pos(path, strlen(path));
	if (pos < 0) {
		pos = -pos-1;
		active_nr--;
		if (pos < active_nr)
			memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos - 1) * sizeof(struct cache_entry *));
	}
}

static int add_cache_entry(struct cache_entry *ce)
{
	int pos;

	pos = cache_name_pos(ce->name, ce->namelen);

	/* existing match? Just replace it */
	if (pos < 0) {
		active_cache[-pos-1] = ce;
		return 0;
	}

	/* Make sure the array is big enough .. */
	if (active_nr == active_alloc) {
		active_alloc = alloc_nr(active_alloc);
		active_cache = realloc(active_cache, active_alloc * sizeof(struct cache_entry *));
	}

	/* Add it in.. */
	active_nr++;
	if (active_nr > pos)
		memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
	active_cache[pos] = ce;
	return 0;
}

static int index_fd(const char *path, int namelen, struct cache_entry *ce, int fd, struct stat *st)
{
	z_stream stream;
	int max_out_bytes = namelen + st->st_size + 200;
	void *out = malloc(max_out_bytes);
	void *metadata = malloc(namelen + 200);
	void *in = mmap(NULL, st->st_size, PROT_READ, MAP_PRIVATE, fd, 0);
	SHA_CTX c;

	close(fd);
	if (!out || (int)(long)in == -1)
		return -1;

	memset(&stream, 0, sizeof(stream));
	deflateInit(&stream, Z_BEST_COMPRESSION);

	/*
	 * ASCII size + nul byte
	 */	
	stream.next_in = metadata;
	stream.avail_in = 1+sprintf(metadata, "blob %lu", (unsigned long) st->st_size);
	stream.next_out = out;
	stream.avail_out = max_out_bytes;
	while (deflate(&stream, 0) == Z_OK)
		/* nothing */;

	/*
	 * File content
	 */
	stream.next_in = in;
	stream.avail_in = st->st_size;
	while (deflate(&stream, Z_FINISH) == Z_OK)
		/*nothing */;

	deflateEnd(&stream);
	
	SHA1_Init(&c);
	SHA1_Update(&c, out, stream.total_out);
	SHA1_Final(ce->sha1, &c);

	return write_sha1_buffer(ce->sha1, out, stream.total_out);
}

static int add_file_to_cache(char *path)
{
	int size, namelen;
	struct cache_entry *ce;
	struct stat st;
	int fd;

	fd = open(path, O_RDONLY);
	if (fd < 0) {
		if (errno == ENOENT)
			return remove_file_from_cache(path);
		return -1;
	}
	if (fstat(fd, &st) < 0) {
		close(fd);
		return -1;
	}
	namelen = strlen(path);
	size = cache_entry_size(namelen);
	ce = malloc(size);
	memset(ce, 0, size);
	memcpy(ce->name, path, namelen);
	ce->ctime.sec = st.st_ctime;
	ce->ctime.nsec = st.st_ctim.tv_nsec;
	ce->mtime.sec = st.st_mtime;
	ce->mtime.nsec = st.st_mtim.tv_nsec;
	ce->st_dev = st.st_dev;
	ce->st_ino = st.st_ino;
	ce->st_mode = st.st_mode;
	ce->st_uid = st.st_uid;
	ce->st_gid = st.st_gid;
	ce->st_size = st.st_size;
	ce->namelen = namelen;

	if (index_fd(path, namelen, ce, fd, &st) < 0)
		return -1;

	return add_cache_entry(ce);
}

static int write_cache(int newfd, struct cache_entry **cache, int entries)
{
	SHA_CTX c;
	struct cache_header hdr;
	int i;

	hdr.signature = CACHE_SIGNATURE;
	hdr.version = 1;
	hdr.entries = entries;

	SHA1_Init(&c);
	SHA1_Update(&c, &hdr, offsetof(struct cache_header, sha1));
	for (i = 0; i < entries; i++) {
		struct cache_entry *ce = cache[i];
		int size = ce_size(ce);
		SHA1_Update(&c, ce, size);
	}
	SHA1_Final(hdr.sha1, &c);

	if (write(newfd, &hdr, sizeof(hdr)) != sizeof(hdr))
		return -1;

	for (i = 0; i < entries; i++) {
		struct cache_entry *ce = cache[i];
		int size = ce_size(ce);
		if (write(newfd, ce, size) != size)
			return -1;
	}
	return 0;
}		

/*
 * We fundamentally don't like some paths: we don't want
 * dot or dot-dot anywhere, and in fact, we don't even want
 * any other dot-files (.dircache or anything else). They
 * are hidden, for chist sake.
 *
 * Also, we don't want double slashes or slashes at the
 * end that can make pathnames ambiguous. 
 */
static int verify_path(char *path)
{
	char c;

	goto inside;
	for (;;) {
		if (!c)
			return 1;
		if (c == '/') {
inside:
			c = *path++;
			if (c != '/' && c != '.' && c != '\0')
				continue;
			return 0;
		}
		c = *path++;
	}
}

int main(int argc, char **argv)
{
	int i, newfd, entries;

	entries = read_cache();
	if (entries < 0) {
		perror("cache corrupted");
		return -1;
	}

	newfd = open(".dircache/index.lock", O_RDWR | O_CREAT | O_EXCL, 0600);
	if (newfd < 0) {
		perror("unable to create new cachefile");
		return -1;
	}
	for (i = 1 ; i < argc; i++) {
		char *path = argv[i];
		if (!verify_path(path)) {
			fprintf(stderr, "Ignoring path %s\n", argv[i]);
			continue;
		}
		if (add_file_to_cache(path)) {
			fprintf(stderr, "Unable to add %s to database\n", path);
			goto out;
		}
	}
	if (!write_cache(newfd, active_cache, active_nr) && !rename(".dircache/index.lock", ".dircache/index"))
		return 0;
out:
	unlink(".dircache/index.lock");
}

#include "cache.h"

const char *sha1_file_directory = NULL;
struct cache_entry **active_cache = NULL;
unsigned int active_nr = 0, active_alloc = 0;

void usage(const char *err)
{
	fprintf(stderr, "read-tree: %s\n", err);
	exit(1);
}

static unsigned hexval(char c)
{
	if (c >= '0' && c <= '9')
		return c - '0';
	if (c >= 'a' && c <= 'f')
		return c - 'a' + 10;
	if (c >= 'A' && c <= 'F')
		return c - 'A' + 10;
	return ~0;
}

int get_sha1_hex(char *hex, unsigned char *sha1)
{
	int i;
	for (i = 0; i < 20; i++) {
		unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
		if (val & ~0xff)
			return -1;
		*sha1++ = val;
		hex += 2;
	}
	return 0;
}

char * sha1_to_hex(unsigned char *sha1)
{
	static char buffer[50];
	static const char hex[] = "0123456789abcdef";
	char *buf = buffer;
	int i;

	for (i = 0; i < 20; i++) {
		unsigned int val = *sha1++;
		*buf++ = hex[val >> 4];
		*buf++ = hex[val & 0xf];
	}
	return buffer;
}

/*
 * NOTE! This returns a statically allocated buffer, so you have to be
 * careful about using it. Do a "strdup()" if you need to save the
 * filename.
 */
char *sha1_file_name(unsigned char *sha1)
{
	int i;
	static char *name, *base;

	if (!base) {
		char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
		int len = strlen(sha1_file_directory);
		base = malloc(len + 60);
		memcpy(base, sha1_file_directory, len);
		memset(base+len, 0, 60);
		base[len] = '/';
		base[len+3] = '/';
		name = base + len + 1;
	}
	for (i = 0; i < 20; i++) {
		static char hex[] = "0123456789abcdef";
		unsigned int val = sha1[i];
		char *pos = name + i*2 + (i > 0);
		*pos++ = hex[val >> 4];
		*pos = hex[val & 0xf];
	}
	return base;
}

void * read_sha1_file(unsigned char *sha1, char *type, unsigned long *size)
{
	z_stream stream;
	char buffer[8192];
	struct stat st;
	int i, fd, ret, bytes;
	void *map, *buf;
	char *filename = sha1_file_name(sha1);

	fd = open(filename, O_RDONLY);
	if (fd < 0) {
		perror(filename);
		return NULL;
	}
	if (fstat(fd, &st) < 0) {
		close(fd);
		return NULL;
	}
	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
	close(fd);
	if (-1 == (int)(long)map)
		return NULL;

	/* Get the data stream */
	memset(&stream, 0, sizeof(stream));
	stream.next_in = map;
	stream.avail_in = st.st_size;
	stream.next_out = buffer;
	stream.avail_out = sizeof(buffer);

	inflateInit(&stream);
	ret = inflate(&stream, 0);
	if (sscanf(buffer, "%10s %lu", type, size) != 2)
		return NULL;
	bytes = strlen(buffer) + 1;
	buf = malloc(*size);
	if (!buf)
		return NULL;

	memcpy(buf, buffer + bytes, stream.total_out - bytes);
	bytes = stream.total_out - bytes;
	if (bytes < *size && ret == Z_OK) {
		stream.next_out = buf + bytes;
		stream.avail_out = *size - bytes;
		while (inflate(&stream, Z_FINISH) == Z_OK)
			/* nothing */;
	}
	inflateEnd(&stream);
	return buf;
}

int write_sha1_file(char *buf, unsigned len)
{
	int size;
	char *compressed;
	z_stream stream;
	unsigned char sha1[20];
	SHA_CTX c;

	/* Set it up */
	memset(&stream, 0, sizeof(stream));
	deflateInit(&stream, Z_BEST_COMPRESSION);
	size = deflateBound(&stream, len);
	compressed = malloc(size);

	/* Compress it */
	stream.next_in = buf;
	stream.avail_in = len;
	stream.next_out = compressed;
	stream.avail_out = size;
	while (deflate(&stream, Z_FINISH) == Z_OK)
		/* nothing */;
	deflateEnd(&stream);
	size = stream.total_out;

	/* Sha1.. */
	SHA1_Init(&c);
	SHA1_Update(&c, compressed, size);
	SHA1_Final(sha1, &c);

	if (write_sha1_buffer(sha1, compressed, size) < 0)
		return -1;
	printf("%s\n", sha1_to_hex(sha1));
	return 0;
}

int write_sha1_buffer(unsigned char *sha1, void *buf, unsigned int size)
{
	char *filename = sha1_file_name(sha1);
	int i, fd;

	fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
	if (fd < 0)
		return (errno == EEXIST) ? 0 : -1;
	write(fd, buf, size);
	close(fd);
	return 0;
}

static int error(const char * string)
{
	fprintf(stderr, "error: %s\n", string);
	return -1;
}

static int verify_hdr(struct cache_header *hdr, unsigned long size)
{
	SHA_CTX c;
	unsigned char sha1[20];

	if (hdr->signature != CACHE_SIGNATURE)
		return error("bad signature");
	if (hdr->version != 1)
		return error("bad version");
	SHA1_Init(&c);
	SHA1_Update(&c, hdr, offsetof(struct cache_header, sha1));
	SHA1_Update(&c, hdr+1, size - sizeof(*hdr));
	SHA1_Final(sha1, &c);
	if (memcmp(sha1, hdr->sha1, 20))
		return error("bad header sha1");
	return 0;
}

int read_cache(void)
{
	int fd, i;
	struct stat st;
	unsigned long size, offset;
	void *map;
	struct cache_header *hdr;

	errno = EBUSY;
	if (active_cache)
		return error("more than one cachefile");
	errno = ENOENT;
	sha1_file_directory = getenv(DB_ENVIRONMENT);
	if (!sha1_file_directory)
		sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
	if (access(sha1_file_directory, X_OK) < 0)
		return error("no access to SHA1 file directory");
	fd = open(".dircache/index", O_RDONLY);
	if (fd < 0)
		return (errno == ENOENT) ? 0 : error("open failed");

	map = (void *)-1;
	if (!fstat(fd, &st)) {
		map = NULL;
		size = st.st_size;
		errno = EINVAL;
		if (size > sizeof(struct cache_header))
			map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
	}
	close(fd);
	if (-1 == (int)(long)map)
		return error("mmap failed");

	hdr = map;
	if (verify_hdr(hdr, size) < 0)
		goto unmap;

	active_nr = hdr->entries;
	active_alloc = alloc_nr(active_nr);
	active_cache = calloc(active_alloc, sizeof(struct cache_entry *));

	offset = sizeof(*hdr);
	for (i = 0; i < hdr->entries; i++) {
		struct cache_entry *ce = map + offset;
		offset = offset + ce_size(ce);
		active_cache[i] = ce;
	}
	return active_nr;

unmap:
	munmap(map, size);
	errno = EINVAL;
	return error("verify header failed");
}

#include "cache.h"

static int unpack(unsigned char *sha1)
{
	void *buffer;
	unsigned long size;
	char type[20];

	buffer = read_sha1_file(sha1, type, &size);
	if (!buffer)
		usage("unable to read sha1 file");
	if (strcmp(type, "tree"))
		usage("expected a 'tree' node");
	while (size) {
		int len = strlen(buffer)+1;
		unsigned char *sha1 = buffer + len;
		char *path = strchr(buffer, ' ')+1;
		unsigned int mode;
		if (size < len + 20 || sscanf(buffer, "%o", &mode) != 1)
			usage("corrupt 'tree' file");
		buffer = sha1 + 20;
		size -= len + 20;
		printf("%o %s (%s)\n", mode, path, sha1_to_hex(sha1));
	}
	return 0;
}

int main(int argc, char **argv)
{
	int fd;
	unsigned char sha1[20];

	if (argc != 2)
		usage("read-tree <key>");
	if (get_sha1_hex(argv[1], sha1) < 0)
		usage("read-tree <key>");
	sha1_file_directory = getenv(DB_ENVIRONMENT);
	if (!sha1_file_directory)
		sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
	if (unpack(sha1) < 0)
		usage("unpack failed");
	return 0;
}

#include "cache.h"

static int check_valid_sha1(unsigned char *sha1)
{
	char *filename = sha1_file_name(sha1);
	int ret;

	/* If we were anal, we'd check that the sha1 of the contents actually matches */
	ret = access(filename, R_OK);
	if (ret)
		perror(filename);
	return ret;
}

static int prepend_integer(char *buffer, unsigned val, int i)
{
	buffer[--i] = '\0';
	do {
		buffer[--i] = '0' + (val % 10);
		val /= 10;
	} while (val);
	return i;
}

#define ORIG_OFFSET (40)	/* Enough space to add the header of "tree <size>\0" */

int main(int argc, char **argv)
{
	unsigned long size, offset, val;
	int i, entries = read_cache();
	char *buffer;

	if (entries <= 0) {
		fprintf(stderr, "No file-cache to create a tree of\n");
		exit(1);
	}

	/* Guess at an initial size */
	size = entries * 40 + 400;
	buffer = malloc(size);
	offset = ORIG_OFFSET;

	for (i = 0; i < entries; i++) {
		struct cache_entry *ce = active_cache[i];
		if (check_valid_sha1(ce->sha1) < 0)
			exit(1);
		if (offset + ce->namelen + 60 > size) {
			size = alloc_nr(offset + ce->namelen + 60);
			buffer = realloc(buffer, size);
		}
		offset += sprintf(buffer + offset, "%o %s", ce->st_mode, ce->name);
		buffer[offset++] = 0;
		memcpy(buffer + offset, ce->sha1, 20);
		offset += 20;
	}

	i = prepend_integer(buffer, offset - ORIG_OFFSET, ORIG_OFFSET);
	i -= 5;
	memcpy(buffer+i, "tree ", 5);

	buffer += i;
	offset -= i;

	write_sha1_file(buffer, offset);
	return 0;
}

$ echo "test commit message" | ./commit-tree <tree-SHA1> -p <parent-commit-SHA1> ... 

#include "cache.h"

#include <pwd.h>
#include <time.h>

#define BLOCKING (1ul << 14)
#define ORIG_OFFSET (40)

/*
 * Leave space at the beginning to insert the tag
 * once we know how big things are.
 *
 * FIXME! Share the code with "write-tree.c"
 */
static void init_buffer(char **bufp, unsigned int *sizep)
{
	char *buf = malloc(BLOCKING);
	memset(buf, 0, ORIG_OFFSET);
	*sizep = ORIG_OFFSET;
	*bufp = buf;
}

static void add_buffer(char **bufp, unsigned int *sizep, const char *fmt, ...)
{
	char one_line[2048];
	va_list args;
	int len;
	unsigned long alloc, size, newsize;
	char *buf;

	va_start(args, fmt);
	len = vsnprintf(one_line, sizeof(one_line), fmt, args);
	va_end(args);
	size = *sizep;
	newsize = size + len;
	alloc = (size + 32767) & ~32767;
	buf = *bufp;
	if (newsize > alloc) {
		alloc = (newsize + 32767) & ~32767;   
		buf = realloc(buf, alloc);
		*bufp = buf;
	}
	*sizep = newsize;
	memcpy(buf + size, one_line, len);
}

static int prepend_integer(char *buffer, unsigned val, int i)
{
	buffer[--i] = '\0';
	do {
		buffer[--i] = '0' + (val % 10);
		val /= 10;
	} while (val);
	return i;
}

static void finish_buffer(char *tag, char **bufp, unsigned int *sizep)
{
	int taglen;
	int offset;
	char *buf = *bufp;
	unsigned int size = *sizep;

	offset = prepend_integer(buf, size - ORIG_OFFSET, ORIG_OFFSET);
	taglen = strlen(tag);
	offset -= taglen;
	buf += offset;
	size -= offset;
	memcpy(buf, tag, taglen);

	*bufp = buf;
	*sizep = size;
}

static void remove_special(char *p)
{
	char c;
	char *dst = p;

	for (;;) {
		c = *p;
		p++;
		switch(c) {
		case '\n': case '<': case '>':
			continue;
		}
		*dst++ = c;
		if (!c)
			break;
	}
}

/*
 * Having more than two parents may be strange, but hey, there's
 * no conceptual reason why the file format couldn't accept multi-way
 * merges. It might be the "union" of several packages, for example.
 *
 * I don't really expect that to happen, but this is here to make
 * it clear that _conceptually_ it's ok..
 */
#define MAXPARENT (16)

int main(int argc, char **argv)
{
	int i, len;
	int parents = 0;
	unsigned char tree_sha1[20];
	unsigned char parent_sha1[MAXPARENT][20];
	char *gecos, *realgecos;
	char *email, realemail[1000];
	char *date, *realdate;
	char comment[1000];
	struct passwd *pw;
	time_t now;
	char *buffer;
	unsigned int size;

	if (argc < 2 || get_sha1_hex(argv[1], tree_sha1) < 0)
		usage("commit-tree <sha1> [-p <sha1>]* < changelog");

	for (i = 2; i < argc; i += 2) {
		char *a, *b;
		a = argv[i]; b = argv[i+1];
		if (!b || strcmp(a, "-p") || get_sha1_hex(b, parent_sha1[parents]))
			usage("commit-tree <sha1> [-p <sha1>]* < changelog");
		parents++;
	}
	if (!parents)
		fprintf(stderr, "Committing initial tree %s\n", argv[1]);
	pw = getpwuid(getuid());
	if (!pw)
		usage("You don't exist. Go away!");
	realgecos = pw->pw_gecos;
	len = strlen(pw->pw_name);
	memcpy(realemail, pw->pw_name, len);
	realemail[len] = '@';
	gethostname(realemail+len+1, sizeof(realemail)-len-1);
	time(&now);
	realdate = ctime(&now);

	gecos = getenv("COMMITTER_NAME") ? : realgecos;
	email = getenv("COMMITTER_EMAIL") ? : realemail;
	date = getenv("COMMITTER_DATE") ? : realdate;

	remove_special(gecos); remove_special(realgecos);
	remove_special(email); remove_special(realemail);
	remove_special(date); remove_special(realdate);

	init_buffer(&buffer, &size);
	add_buffer(&buffer, &size, "tree %s\n", sha1_to_hex(tree_sha1));

	/*
	 * NOTE! This ordering means that the same exact tree merged with a
	 * different order of parents will be a _different_ changeset even
	 * if everything else stays the same.
	 */
	for (i = 0; i < parents; i++)
		add_buffer(&buffer, &size, "parent %s\n", sha1_to_hex(parent_sha1[i]));

	/* Person/date information */
	add_buffer(&buffer, &size, "author %s <%s> %s\n", gecos, email, date);
	add_buffer(&buffer, &size, "committer %s <%s> %s\n\n", realgecos, realemail, realdate);

	/* And add the comment */
	while (fgets(comment, sizeof(comment), stdin) != NULL)
		add_buffer(&buffer, &size, "%s", comment);

	finish_buffer("commit ", &buffer, &size);

	write_sha1_file(buffer, size);
	return 0;
}

#include "cache.h"

#define MTIME_CHANGED	0x0001
#define CTIME_CHANGED	0x0002
#define OWNER_CHANGED	0x0004
#define MODE_CHANGED    0x0008
#define INODE_CHANGED   0x0010
#define DATA_CHANGED    0x0020

static int match_stat(struct cache_entry *ce, struct stat *st)
{
	unsigned int changed = 0;

	if (ce->mtime.sec  != (unsigned int)st->st_mtim.tv_sec ||
	    ce->mtime.nsec != (unsigned int)st->st_mtim.tv_nsec)
		changed |= MTIME_CHANGED;
	if (ce->ctime.sec  != (unsigned int)st->st_ctim.tv_sec ||
	    ce->ctime.nsec != (unsigned int)st->st_ctim.tv_nsec)
		changed |= CTIME_CHANGED;
	if (ce->st_uid != (unsigned int)st->st_uid ||
	    ce->st_gid != (unsigned int)st->st_gid)
		changed |= OWNER_CHANGED;
	if (ce->st_mode != (unsigned int)st->st_mode)
		changed |= MODE_CHANGED;
	if (ce->st_dev != (unsigned int)st->st_dev ||
	    ce->st_ino != (unsigned int)st->st_ino)
		changed |= INODE_CHANGED;
	if (ce->st_size != (unsigned int)st->st_size)
		changed |= DATA_CHANGED;
	return changed;
}

static void show_differences(struct cache_entry *ce, struct stat *cur,
	void *old_contents, unsigned long long old_size)
{
	static char cmd[1000];
	FILE *f;

	snprintf(cmd, sizeof(cmd), "diff -u - %s", ce->name);
	f = popen(cmd, "w");
	fwrite(old_contents, old_size, 1, f);
	pclose(f);
}

int main(int argc, char **argv)
{
	int entries = read_cache();
	int i;

	if (entries < 0) {
		perror("read_cache");
		exit(1);
	}
	for (i = 0; i < entries; i++) {
		struct stat st;
		struct cache_entry *ce = active_cache[i];
		int n, changed;
		unsigned int mode;
		unsigned long size;
		char type[20];
		void *new;

		if (stat(ce->name, &st) < 0) {
			printf("%s: %s\n", ce->name, strerror(errno));
			continue;
		}
		changed = match_stat(ce, &st);
		if (!changed) {
			printf("%s: ok\n", ce->name);
			continue;
		}
		printf("%.*s:  ", ce->namelen, ce->name);
		for (n = 0; n < 20; n++)
			printf("%02x", ce->sha1[n]);
		printf("\n");
		new = read_sha1_file(ce->sha1, type, &size);
		show_differences(ce, &st, new, size);
		free(new);
	}
	return 0;
}

#include "cache.h"

int main(int argc, char **argv)
{
	unsigned char sha1[20];
	char type[20];
	void *buf;
	unsigned long size;
	char template[] = "temp_git_file_XXXXXX";
	int fd;

	if (argc != 2 || get_sha1_hex(argv[1], sha1))
		usage("cat-file: cat-file <sha1>");
	buf = read_sha1_file(sha1, type, &size);
	if (!buf)
		exit(1);
	fd = mkstemp(template);
	if (fd < 0)
		usage("unable to create tempfile");
	if (write(fd, buf, size) != size)
		strcpy(type, "bad");
	printf("%s: %s\n", template, type);
}