X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=read-cache.c;h=c499c5185678b6b4ac35d57d1ab0b36cc2ff056b;hb=4514ad4fb77b3c68f69133c22b9c0d3b88ff058f;hp=24ebe383d7a4e72c8cd461f90b4b06bf5cfdb0d1;hpb=6b0c3121061df6b323f430700e8077b324b5e9dd;p=git.git

diff --git a/read-cache.c b/read-cache.c
index 24ebe383..c499c518 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -4,10 +4,26 @@
  * Copyright (C) Linus Torvalds, 2005
  */
 #include "cache.h"
+#include "cache-tree.h"
+
+/* Index extensions.
+ *
+ * The first letter should be 'A'..'Z' for extensions that are not
+ * necessary for a correct operation (i.e. optimization data).
+ * When new extensions are added that _needs_ to be understood in
+ * order to correctly interpret the index file, pick character that
+ * is outside the range, to cause the reader to abort.
+ */
+
+#define CACHE_EXT(s) ( (s[0]<<24)|(s[1]<<16)|(s[2]<<8)|(s[3]) )
+#define CACHE_EXT_TREE 0x54524545	/* "TREE" */
 
 struct cache_entry **active_cache = NULL;
+static time_t index_file_timestamp;
 unsigned int active_nr = 0, active_alloc = 0, active_cache_changed = 0;
 
+struct cache_tree *active_cache_tree = NULL;
+
 /*
  * This only updates the "non-critical" parts of the directory
  * cache, ie the parts that aren't tracked by GIT, and only used
@@ -17,7 +33,7 @@ void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
 {
 	ce->ce_ctime.sec = htonl(st->st_ctime);
 	ce->ce_mtime.sec = htonl(st->st_mtime);
-#ifdef NSEC
+#ifdef USE_NSEC
 	ce->ce_ctime.nsec = htonl(st->st_ctim.tv_nsec);
 	ce->ce_mtime.nsec = htonl(st->st_mtim.tv_nsec);
 #endif
@@ -26,17 +42,81 @@ void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
 	ce->ce_uid = htonl(st->st_uid);
 	ce->ce_gid = htonl(st->st_gid);
 	ce->ce_size = htonl(st->st_size);
+
+	if (assume_unchanged)
+		ce->ce_flags |= htons(CE_VALID);
+}
+
+static int ce_compare_data(struct cache_entry *ce, struct stat *st)
+{
+	int match = -1;
+	int fd = open(ce->name, O_RDONLY);
+
+	if (fd >= 0) {
+		unsigned char sha1[20];
+		if (!index_fd(sha1, fd, st, 0, NULL))
+			match = memcmp(sha1, ce->sha1, 20);
+		close(fd);
+	}
+	return match;
+}
+
+static int ce_compare_link(struct cache_entry *ce, unsigned long expected_size)
+{
+	int match = -1;
+	char *target;
+	void *buffer;
+	unsigned long size;
+	char type[10];
+	int len;
+
+	target = xmalloc(expected_size);
+	len = readlink(ce->name, target, expected_size);
+	if (len != expected_size) {
+		free(target);
+		return -1;
+	}
+	buffer = read_sha1_file(ce->sha1, type, &size);
+	if (!buffer) {
+		free(target);
+		return -1;
+	}
+	if (size == expected_size)
+		match = memcmp(buffer, target, size);
+	free(buffer);
+	free(target);
+	return match;
+}
+
+static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
+{
+	switch (st->st_mode & S_IFMT) {
+	case S_IFREG:
+		if (ce_compare_data(ce, st))
+			return DATA_CHANGED;
+		break;
+	case S_IFLNK:
+		if (ce_compare_link(ce, st->st_size))
+			return DATA_CHANGED;
+		break;
+	default:
+		return TYPE_CHANGED;
+	}
+	return 0;
 }
 
-int ce_match_stat(struct cache_entry *ce, struct stat *st)
+static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 {
 	unsigned int changed = 0;
 
 	switch (ntohl(ce->ce_mode) & S_IFMT) {
 	case S_IFREG:
 		changed |= !S_ISREG(st->st_mode) ? TYPE_CHANGED : 0;
-		/* We consider only the owner x bit to be relevant for "mode changes" */
-		if (0100 & (ntohl(ce->ce_mode) ^ st->st_mode))
+		/* We consider only the owner x bit to be relevant for
+		 * "mode changes"
+		 */
+		if (trust_executable_bit &&
+		    (0100 & (ntohl(ce->ce_mode) ^ st->st_mode)))
 			changed |= MODE_CHANGED;
 		break;
 	case S_IFLNK:
@@ -50,7 +130,7 @@ int ce_match_stat(struct cache_entry *ce, struct stat *st)
 	if (ce->ce_ctime.sec != htonl(st->st_ctime))
 		changed |= CTIME_CHANGED;
 
-#ifdef NSEC
+#ifdef USE_NSEC
 	/*
 	 * nsec seems unreliable - not all filesystems support it, so
 	 * as long as it is in the inode cache you get right nsec
@@ -65,14 +145,88 @@ int ce_match_stat(struct cache_entry *ce, struct stat *st)
 	if (ce->ce_uid != htonl(st->st_uid) ||
 	    ce->ce_gid != htonl(st->st_gid))
 		changed |= OWNER_CHANGED;
-	if (ce->ce_dev != htonl(st->st_dev) ||
-	    ce->ce_ino != htonl(st->st_ino))
+	if (ce->ce_ino != htonl(st->st_ino))
 		changed |= INODE_CHANGED;
+
+#ifdef USE_STDEV
+	/*
+	 * st_dev breaks on network filesystems where different
+	 * clients will have different views of what "device"
+	 * the filesystem is on
+	 */
+	if (ce->ce_dev != htonl(st->st_dev))
+		changed |= INODE_CHANGED;
+#endif
+
 	if (ce->ce_size != htonl(st->st_size))
 		changed |= DATA_CHANGED;
+
 	return changed;
 }
 
+int ce_match_stat(struct cache_entry *ce, struct stat *st, int ignore_valid)
+{
+	unsigned int changed;
+
+	/*
+	 * If it's marked as always valid in the index, it's
+	 * valid whatever the checked-out copy says.
+	 */
+	if (!ignore_valid && (ce->ce_flags & htons(CE_VALID)))
+		return 0;
+
+	changed = ce_match_stat_basic(ce, st);
+
+	/*
+	 * Within 1 second of this sequence:
+	 * 	echo xyzzy >file && git-update-index --add file
+	 * running this command:
+	 * 	echo frotz >file
+	 * would give a falsely clean cache entry.  The mtime and
+	 * length match the cache, and other stat fields do not change.
+	 *
+	 * We could detect this at update-index time (the cache entry
+	 * being registered/updated records the same time as "now")
+	 * and delay the return from git-update-index, but that would
+	 * effectively mean we can make at most one commit per second,
+	 * which is not acceptable.  Instead, we check cache entries
+	 * whose mtime are the same as the index file timestamp more
+	 * carefully than others.
+	 */
+	if (!changed &&
+	    index_file_timestamp &&
+	    index_file_timestamp <= ntohl(ce->ce_mtime.sec))
+		changed |= ce_modified_check_fs(ce, st);
+
+	return changed;
+}
+
+int ce_modified(struct cache_entry *ce, struct stat *st, int really)
+{
+	int changed, changed_fs;
+	changed = ce_match_stat(ce, st, really);
+	if (!changed)
+		return 0;
+	/*
+	 * If the mode or type has changed, there's no point in trying
+	 * to refresh the entry - it's not going to match
+	 */
+	if (changed & (MODE_CHANGED | TYPE_CHANGED))
+		return changed;
+
+	/* Immediately after read-tree or update-index --cacheinfo,
+	 * the length field is zero.  For other cases the ce_size
+	 * should match the SHA1 recorded in the index entry.
+	 */
+	if ((changed & DATA_CHANGED) && ce->ce_size != htonl(0))
+		return changed;
+
+	changed_fs = ce_modified_check_fs(ce, st);
+	if (changed_fs)
+		return changed | changed_fs;
+	return 0;
+}
+
 int base_name_compare(const char *name1, int len1, int mode1,
 		      const char *name2, int len2, int mode2)
 {
@@ -106,6 +260,11 @@ int cache_name_compare(const char *name1, int flags1, const char *name2, int fla
 		return -1;
 	if (len1 > len2)
 		return 1;
+
+	/* Compare stages  */
+	flags1 &= CE_STAGEMASK;
+	flags2 &= CE_STAGEMASK;
+
 	if (flags1 < flags2)
 		return -1;
 	if (flags1 > flags2)
@@ -122,7 +281,7 @@ int cache_name_pos(const char *name, int namelen)
 	while (last > first) {
 		int next = (last + first) >> 1;
 		struct cache_entry *ce = active_cache[next];
-		int cmp = cache_name_compare(name, namelen, ce->name, htons(ce->ce_flags));
+		int cmp = cache_name_compare(name, namelen, ce->name, ntohs(ce->ce_flags));
 		if (!cmp)
 			return next;
 		if (cmp < 0) {
@@ -145,7 +304,7 @@ int remove_cache_entry_at(int pos)
 	return 1;
 }
 
-int remove_file_from_cache(char *path)
+int remove_file_from_cache(const char *path)
 {
 	int pos = cache_name_pos(path, strlen(path));
 	if (pos < 0)
@@ -161,105 +320,204 @@ int ce_same_name(struct cache_entry *a, struct cache_entry *b)
 	return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 }
 
-/* We may be in a situation where we already have path/file and path
- * is being added, or we already have path and path/file is being
- * added.  Either one would result in a nonsense tree that has path
- * twice when git-write-tree tries to write it out.  Prevent it.
- * 
- * If ok-to-replace is specified, we remove the conflicting entries
- * from the cache so the caller should recompute the insert position.
- * When this happens, we return non-zero.
- */
-static int check_file_directory_conflict(const struct cache_entry *ce,
-					 int ok_to_replace)
+int ce_path_match(const struct cache_entry *ce, const char **pathspec)
 {
-	int pos, replaced = 0;
-	const char *path = ce->name;
-	int namelen = strlen(path);
-	int stage = ce_stage(ce);
-	char *pathbuf = xmalloc(namelen + 1);
-	char *cp;
+	const char *match, *name;
+	int len;
+
+	if (!pathspec)
+		return 1;
 
-	memcpy(pathbuf, path, namelen + 1);
+	len = ce_namelen(ce);
+	name = ce->name;
+	while ((match = *pathspec++) != NULL) {
+		int matchlen = strlen(match);
+		if (matchlen > len)
+			continue;
+		if (memcmp(name, match, matchlen))
+			continue;
+		if (matchlen && name[matchlen-1] == '/')
+			return 1;
+		if (name[matchlen] == '/' || !name[matchlen])
+			return 1;
+		if (!matchlen)
+			return 1;
+	}
+	return 0;
+}
 
+/*
+ * We fundamentally don't like some paths: we don't want
+ * dot or dot-dot anywhere, and for obvious reasons don't
+ * want to recurse into ".git" either.
+ *
+ * Also, we don't want double slashes or slashes at the
+ * end that can make pathnames ambiguous.
+ */
+static int verify_dotfile(const char *rest)
+{
 	/*
-	 * We are inserting path/file.  Do they have path registered at
-	 * the same stage?  We need to do this for all the levels of our
-	 * subpath.
+	 * The first character was '.', but that
+	 * has already been discarded, we now test
+	 * the rest.
 	 */
-	cp = pathbuf;
-	while (1) {
-		char *ep = strchr(cp, '/');
-		if (!ep)
+	switch (*rest) {
+	/* "." is not allowed */
+	case '\0': case '/':
+		return 0;
+
+	/*
+	 * ".git" followed by  NUL or slash is bad. This
+	 * shares the path end test with the ".." case.
+	 */
+	case 'g':
+		if (rest[1] != 'i')
 			break;
-		*ep = 0;    /* first cut it at slash */
-		pos = cache_name_pos(pathbuf,
-				     htons(create_ce_flags(ep-cp, stage)));
-		if (0 <= pos) {
-			/* Our leading path component is registered as a file,
-			 * and we are trying to make it a directory.  This is
-			 * bad.
-			 */
-			if (!ok_to_replace) {
-				free(pathbuf);
-				return -1;
+		if (rest[2] != 't')
+			break;
+		rest += 2;
+	/* fallthrough */
+	case '.':
+		if (rest[1] == '\0' || rest[1] == '/')
+			return 0;
+	}
+	return 1;
+}
+
+int verify_path(const char *path)
+{
+	char c;
+
+	goto inside;
+	for (;;) {
+		if (!c)
+			return 1;
+		if (c == '/') {
+inside:
+			c = *path++;
+			switch (c) {
+			default:
+				continue;
+			case '/': case '\0':
+				break;
+			case '.':
+				if (verify_dotfile(path))
+					continue;
 			}
-			fprintf(stderr, "removing file '%s' to replace it with a directory to create '%s'.\n", pathbuf, path);
-			remove_cache_entry_at(pos);
-			replaced = 1;
+			return 0;
 		}
-		*ep = '/';  /* then restore it and go downwards */
-		cp = ep + 1;
+		c = *path++;
 	}
-	free(pathbuf);
+}
 
-	/* Do we have an entry in the cache that makes our path a prefix
-	 * of it?  That is, are we creating a file where they already expect
-	 * a directory there?
-	 */
-	pos = cache_name_pos(path,
-			     htons(create_ce_flags(namelen, stage)));
+/*
+ * Do we have another file that has the beginning components being a
+ * proper superset of the name we're trying to add?
+ */
+static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replace)
+{
+	int retval = 0;
+	int len = ce_namelen(ce);
+	int stage = ce_stage(ce);
+	const char *name = ce->name;
 
-	/* (0 <= pos) cannot happen because add_cache_entry()
-	 * should have taken care of that case.
-	 */
-	pos = -pos-1;
+	while (pos < active_nr) {
+		struct cache_entry *p = active_cache[pos++];
 
-	/* pos would point at an existing entry that would come immediately
-	 * after our path.  It could be the same as our path in higher stage,
-	 * or different path but in a lower stage.
-	 *
-	 * E.g. when we are inserting path at stage 2,
-	 *
-	 *        1 path
-	 * pos->  3 path
-	 *        2 path/file1
-	 *        3 path/file1
-	 *        2 path/file2
-	 *        2 patho
-	 *
-	 * We need to examine pos, ignore it because it is at different
-	 * stage, examine next to find the path/file at stage 2, and
-	 * complain.  We need to do this until we are not the leading
-	 * path of an existing entry anymore.
-	 */
+		if (len >= ce_namelen(p))
+			break;
+		if (memcmp(name, p->name, len))
+			break;
+		if (ce_stage(p) != stage)
+			continue;
+		if (p->name[len] != '/')
+			continue;
+		retval = -1;
+		if (!ok_to_replace)
+			break;
+		remove_cache_entry_at(--pos);
+	}
+	return retval;
+}
 
-	while (pos < active_nr) {
-		struct cache_entry *other = active_cache[pos];
-		if (strncmp(other->name, path, namelen))
-			break; /* it is not our "subdirectory" anymore */
-		if ((ce_stage(other) == stage) &&
-		    other->name[namelen] == '/') {
-			if (!ok_to_replace)
-				return -1;
-			fprintf(stderr, "removing file '%s' under '%s' to be replaced with a file\n", other->name, path);
+/*
+ * Do we have another file with a pathname that is a proper
+ * subset of the name we're trying to add?
+ */
+static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace)
+{
+	int retval = 0;
+	int stage = ce_stage(ce);
+	const char *name = ce->name;
+	const char *slash = name + ce_namelen(ce);
+
+	for (;;) {
+		int len;
+
+		for (;;) {
+			if (*--slash == '/')
+				break;
+			if (slash <= ce->name)
+				return retval;
+		}
+		len = slash - name;
+
+		pos = cache_name_pos(name, ntohs(create_ce_flags(len, stage)));
+		if (pos >= 0) {
+			retval = -1;
+			if (ok_to_replace)
+				break;
 			remove_cache_entry_at(pos);
-			replaced = 1;
-			continue; /* cycle without updating pos */
+			continue;
+		}
+
+		/*
+		 * Trivial optimization: if we find an entry that
+		 * already matches the sub-directory, then we know
+		 * we're ok, and we can exit.
+		 */
+		pos = -pos-1;
+		while (pos < active_nr) {
+			struct cache_entry *p = active_cache[pos];
+			if ((ce_namelen(p) <= len) ||
+			    (p->name[len] != '/') ||
+			    memcmp(p->name, name, len))
+				break; /* not our subdirectory */
+			if (ce_stage(p) == stage)
+				/* p is at the same stage as our entry, and
+				 * is a subdirectory of what we are looking
+				 * at, so we cannot have conflicts at our
+				 * level or anything shorter.
+				 */
+				return retval;
+			pos++;
 		}
-		pos++;
 	}
-	return replaced;
+	return retval;
+}
+
+/* We may be in a situation where we already have path/file and path
+ * is being added, or we already have path and path/file is being
+ * added.  Either one would result in a nonsense tree that has path
+ * twice when git-write-tree tries to write it out.  Prevent it.
+ * 
+ * If ok-to-replace is specified, we remove the conflicting entries
+ * from the cache so the caller should recompute the insert position.
+ * When this happens, we return non-zero.
+ */
+static int check_file_directory_conflict(const struct cache_entry *ce, int pos, int ok_to_replace)
+{
+	/*
+	 * We check if the path is a sub-path of a subsequent pathname
+	 * first, since removing those will not change the position
+	 * in the array
+	 */
+	int retval = has_file_name(ce, pos, ok_to_replace);
+	/*
+	 * Then check if the path might have a clashing sub-directory
+	 * before it.
+	 */
+	return retval + has_dir_name(ce, pos, ok_to_replace);
 }
 
 int add_cache_entry(struct cache_entry *ce, int option)
@@ -267,9 +525,11 @@ int add_cache_entry(struct cache_entry *ce, int option)
 	int pos;
 	int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 	int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
-	pos = cache_name_pos(ce->name, htons(ce->ce_flags));
+	int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
 
-	/* existing match? Just replace it */
+	pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
+
+	/* existing match? Just replace it. */
 	if (pos >= 0) {
 		active_cache_changed = 1;
 		active_cache[pos] = ce;
@@ -291,11 +551,14 @@ int add_cache_entry(struct cache_entry *ce, int option)
 
 	if (!ok_to_add)
 		return -1;
+	if (!verify_path(ce->name))
+		return -1;
 
-	if (check_file_directory_conflict(ce, ok_to_replace)) {
+	if (!skip_df_check &&
+	    check_file_directory_conflict(ce, pos, ok_to_replace)) {
 		if (!ok_to_replace)
 			return -1;
-		pos = cache_name_pos(ce->name, htons(ce->ce_flags));
+		pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
 		pos = -pos-1;
 	}
 
@@ -314,6 +577,123 @@ int add_cache_entry(struct cache_entry *ce, int option)
 	return 0;
 }
 
+/* Three functions to allow overloaded pointer return; see linux/err.h */
+static inline void *ERR_PTR(long error)
+{
+	return (void *) error;
+}
+
+static inline long PTR_ERR(const void *ptr)
+{
+	return (long) ptr;
+}
+
+static inline long IS_ERR(const void *ptr)
+{
+	return (unsigned long)ptr > (unsigned long)-1000L;
+}
+
+/*
+ * "refresh" does not calculate a new sha1 file or bring the
+ * cache up-to-date for mode/content changes. But what it
+ * _does_ do is to "re-match" the stat information of a file
+ * with the cache, so that you can refresh the cache for a
+ * file that hasn't been changed but where the stat entry is
+ * out of date.
+ *
+ * For example, you'd want to do this after doing a "git-read-tree",
+ * to link up the stat cache details with the proper files.
+ */
+static struct cache_entry *refresh_entry(struct cache_entry *ce, int really)
+{
+	struct stat st;
+	struct cache_entry *updated;
+	int changed, size;
+
+	if (lstat(ce->name, &st) < 0)
+		return ERR_PTR(-errno);
+
+	changed = ce_match_stat(ce, &st, really);
+	if (!changed) {
+		if (really && assume_unchanged &&
+		    !(ce->ce_flags & htons(CE_VALID)))
+			; /* mark this one VALID again */
+		else
+			return NULL;
+	}
+
+	if (ce_modified(ce, &st, really))
+		return ERR_PTR(-EINVAL);
+
+	size = ce_size(ce);
+	updated = xmalloc(size);
+	memcpy(updated, ce, size);
+	fill_stat_cache_info(updated, &st);
+
+	/* In this case, if really is not set, we should leave
+	 * CE_VALID bit alone.  Otherwise, paths marked with
+	 * --no-assume-unchanged (i.e. things to be edited) will
+	 * reacquire CE_VALID bit automatically, which is not
+	 * really what we want.
+	 */
+	if (!really && assume_unchanged && !(ce->ce_flags & htons(CE_VALID)))
+		updated->ce_flags &= ~htons(CE_VALID);
+
+	return updated;
+}
+
+int refresh_cache(unsigned int flags)
+{
+	int i;
+	int has_errors = 0;
+	int really = (flags & REFRESH_REALLY) != 0;
+	int allow_unmerged = (flags & REFRESH_UNMERGED) != 0;
+	int quiet = (flags & REFRESH_QUIET) != 0;
+	int not_new = (flags & REFRESH_IGNORE_MISSING) != 0;
+
+	for (i = 0; i < active_nr; i++) {
+		struct cache_entry *ce, *new;
+		ce = active_cache[i];
+		if (ce_stage(ce)) {
+			while ((i < active_nr) &&
+			       ! strcmp(active_cache[i]->name, ce->name))
+				i++;
+			i--;
+			if (allow_unmerged)
+				continue;
+			printf("%s: needs merge\n", ce->name);
+			has_errors = 1;
+			continue;
+		}
+
+		new = refresh_entry(ce, really);
+		if (!new)
+			continue;
+		if (IS_ERR(new)) {
+			if (not_new && PTR_ERR(new) == -ENOENT)
+				continue;
+			if (really && PTR_ERR(new) == -EINVAL) {
+				/* If we are doing --really-refresh that
+				 * means the index is not valid anymore.
+				 */
+				ce->ce_flags &= ~htons(CE_VALID);
+				active_cache_changed = 1;
+			}
+			if (quiet)
+				continue;
+			printf("%s: needs update\n", ce->name);
+			has_errors = 1;
+			continue;
+		}
+		active_cache_changed = 1;
+		/* You can NOT just free active_cache[i] here, since it
+		 * might not be necessarily malloc()ed but can also come
+		 * from mmap(). */
+		active_cache[i] = new;
+	}
+	return has_errors;
+}
+
 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 {
 	SHA_CTX c;
@@ -331,6 +711,22 @@ static int verify_hdr(struct cache_header *hdr, unsigned long size)
 	return 0;
 }
 
+static int read_index_extension(const char *ext, void *data, unsigned long sz)
+{
+	switch (CACHE_EXT(ext)) {
+	case CACHE_EXT_TREE:
+		active_cache_tree = cache_tree_read(data, sz);
+		break;
+	default:
+		if (*ext < 'A' || 'Z' < *ext)
+			return error("index uses %.4s extension, which we do not understand",
+				     ext);
+		fprintf(stderr, "ignoring %.4s extension\n", ext);
+		break;
+	}
+	return 0;
+}
+
 int read_cache(void)
 {
 	int fd, i;
@@ -341,14 +737,19 @@ int read_cache(void)
 
 	errno = EBUSY;
 	if (active_cache)
-		return error("more than one cachefile");
+		return active_nr;
+
 	errno = ENOENT;
+	index_file_timestamp = 0;
 	fd = open(get_index_file(), O_RDONLY);
-	if (fd < 0)
-		return (errno == ENOENT) ? 0 : error("open failed");
+	if (fd < 0) {
+		if (errno == ENOENT)
+			return 0;
+		die("index file open failed (%s)", strerror(errno));
+	}
 
 	size = 0; // avoid gcc warning
-	map = (void *)-1;
+	map = MAP_FAILED;
 	if (!fstat(fd, &st)) {
 		size = st.st_size;
 		errno = EINVAL;
@@ -356,8 +757,8 @@ int read_cache(void)
 			map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 	}
 	close(fd);
-	if (-1 == (int)(long)map)
-		return error("mmap failed");
+	if (map == MAP_FAILED)
+		die("index file mmap failed (%s)", strerror(errno));
 
 	hdr = map;
 	if (verify_hdr(hdr, size) < 0)
@@ -365,7 +766,7 @@ int read_cache(void)
 
 	active_nr = ntohl(hdr->hdr_entries);
 	active_alloc = alloc_nr(active_nr);
-	active_cache = calloc(active_alloc, sizeof(struct cache_entry *));
+	active_cache = xcalloc(active_alloc, sizeof(struct cache_entry *));
 
 	offset = sizeof(*hdr);
 	for (i = 0; i < active_nr; i++) {
@@ -373,12 +774,29 @@ int read_cache(void)
 		offset = offset + ce_size(ce);
 		active_cache[i] = ce;
 	}
+	index_file_timestamp = st.st_mtime;
+	while (offset <= size - 20 - 8) {
+		/* After an array of active_nr index entries,
+		 * there can be arbitrary number of extended
+		 * sections, each of which is prefixed with
+		 * extension name (4-byte) and section length
+		 * in 4-byte network byte order.
+		 */
+		unsigned long extsize;
+		memcpy(&extsize, map + offset + 4, 4);
+		extsize = ntohl(extsize);
+		if (read_index_extension(map + offset,
+					 map + offset + 8, extsize) < 0)
+			goto unmap;
+		offset += 8;
+		offset += extsize;
+	}
 	return active_nr;
 
 unmap:
 	munmap(map, size);
 	errno = EINVAL;
-	return error("verify header failed");
+	die("index file corrupt");
 }
 
 #define WRITE_BUFFER_SIZE 8192
@@ -407,6 +825,17 @@ static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
  	return 0;
 }
 
+static int write_index_ext_header(SHA_CTX *context, int fd,
+				  unsigned int ext, unsigned int sz)
+{
+	ext = htonl(ext);
+	sz = htonl(sz);
+	if ((ce_write(context, fd, &ext, 4) < 0) ||
+	    (ce_write(context, fd, &sz, 4) < 0))
+		return -1;
+	return 0;
+}
+
 static int ce_flush(SHA_CTX *context, int fd)
 {
 	unsigned int left = write_buffer_len;
@@ -416,6 +845,13 @@ static int ce_flush(SHA_CTX *context, int fd)
 		SHA1_Update(context, write_buffer, left);
 	}
 
+	/* Flush first if not enough space for SHA1 signature */
+	if (left + 20 > WRITE_BUFFER_SIZE) {
+		if (write(fd, write_buffer, left) != left)
+			return -1;
+		left = 0;
+	}
+
 	/* Append the SHA1 signature at the end */
 	SHA1_Final(write_buffer + left, context);
 	left += 20;
@@ -424,15 +860,63 @@ static int ce_flush(SHA_CTX *context, int fd)
 	return 0;
 }
 
+static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
+{
+	/*
+	 * The only thing we care about in this function is to smudge the
+	 * falsely clean entry due to touch-update-touch race, so we leave
+	 * everything else as they are.  We are called for entries whose
+	 * ce_mtime match the index file mtime.
+	 */
+	struct stat st;
+
+	if (lstat(ce->name, &st) < 0)
+		return;
+	if (ce_match_stat_basic(ce, &st))
+		return;
+	if (ce_modified_check_fs(ce, &st)) {
+		/* This is "racily clean"; smudge it.  Note that this
+		 * is a tricky code.  At first glance, it may appear
+		 * that it can break with this sequence:
+		 *
+		 * $ echo xyzzy >frotz
+		 * $ git-update-index --add frotz
+		 * $ : >frotz
+		 * $ sleep 3
+		 * $ echo filfre >nitfol
+		 * $ git-update-index --add nitfol
+		 *
+		 * but it does not.  Whe the second update-index runs,
+		 * it notices that the entry "frotz" has the same timestamp
+		 * as index, and if we were to smudge it by resetting its
+		 * size to zero here, then the object name recorded
+		 * in index is the 6-byte file but the cached stat information
+		 * becomes zero --- which would then match what we would
+		 * obtain from the filesystem next time we stat("frotz"). 
+		 *
+		 * However, the second update-index, before calling
+		 * this function, notices that the cached size is 6
+		 * bytes and what is on the filesystem is an empty
+		 * file, and never calls us, so the cached size information
+		 * for "frotz" stays 6 which does not match the filesystem.
+		 */
+		ce->ce_size = htonl(0);
+	}
+}
+
 int write_cache(int newfd, struct cache_entry **cache, int entries)
 {
 	SHA_CTX c;
 	struct cache_header hdr;
-	int i;
+	int i, removed;
+
+	for (i = removed = 0; i < entries; i++)
+		if (!cache[i]->ce_mode)
+			removed++;
 
 	hdr.hdr_signature = htonl(CACHE_SIGNATURE);
 	hdr.hdr_version = htonl(2);
-	hdr.hdr_entries = htonl(entries);
+	hdr.hdr_entries = htonl(entries - removed);
 
 	SHA1_Init(&c);
 	if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
@@ -440,8 +924,27 @@ int write_cache(int newfd, struct cache_entry **cache, int entries)
 
 	for (i = 0; i < entries; i++) {
 		struct cache_entry *ce = cache[i];
+		if (!ce->ce_mode)
+			continue;
+		if (index_file_timestamp &&
+		    index_file_timestamp <= ntohl(ce->ce_mtime.sec))
+			ce_smudge_racily_clean_entry(ce);
 		if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
 			return -1;
 	}
+
+	/* Write extension data here */
+	if (active_cache_tree) {
+		unsigned long sz;
+		void *data = cache_tree_write(active_cache_tree, &sz);
+		if (data &&
+		    !write_index_ext_header(&c, newfd, CACHE_EXT_TREE, sz) &&
+		    !ce_write(&c, newfd, data, sz))
+			;
+		else {
+			free(data);
+			return -1;
+		}
+	}
 	return ce_flush(&c, newfd);
 }