git/symlinks.c
Clemens Buchacher 1d718a5108 do not overwrite untracked symlinks
Git traditionally overwrites untracked symlinks silently. This will
generally not cause massive data loss, but it is inconsistent with
the behavior for regular files, which are not silently overwritten.

With this change, git refuses to overwrite untracked symlinks by
default. If the user really wants to overwrite the untracked
symlink, he has git-clean and git-checkout -f at his disposal.

Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-02-21 22:51:07 -08:00

304 lines
8.4 KiB
C

#include "cache.h"
/*
* Returns the length (on a path component basis) of the longest
* common prefix match of 'name_a' and 'name_b'.
*/
static int longest_path_match(const char *name_a, int len_a,
const char *name_b, int len_b,
int *previous_slash)
{
int max_len, match_len = 0, match_len_prev = 0, i = 0;
max_len = len_a < len_b ? len_a : len_b;
while (i < max_len && name_a[i] == name_b[i]) {
if (name_a[i] == '/') {
match_len_prev = match_len;
match_len = i;
}
i++;
}
/*
* Is 'name_b' a substring of 'name_a', the other way around,
* or is 'name_a' and 'name_b' the exact same string?
*/
if (i >= max_len && ((len_a > len_b && name_a[len_b] == '/') ||
(len_a < len_b && name_b[len_a] == '/') ||
(len_a == len_b))) {
match_len_prev = match_len;
match_len = i;
}
*previous_slash = match_len_prev;
return match_len;
}
static struct cache_def default_cache;
static inline void reset_lstat_cache(struct cache_def *cache)
{
cache->path[0] = '\0';
cache->len = 0;
cache->flags = 0;
/*
* The track_flags and prefix_len_stat_func members is only
* set by the safeguard rule inside lstat_cache()
*/
}
#define FL_DIR (1 << 0)
#define FL_NOENT (1 << 1)
#define FL_SYMLINK (1 << 2)
#define FL_LSTATERR (1 << 3)
#define FL_ERR (1 << 4)
#define FL_FULLPATH (1 << 5)
/*
* Check if name 'name' of length 'len' has a symlink leading
* component, or if the directory exists and is real, or not.
*
* To speed up the check, some information is allowed to be cached.
* This can be indicated by the 'track_flags' argument, which also can
* be used to indicate that we should check the full path.
*
* The 'prefix_len_stat_func' parameter can be used to set the length
* of the prefix, where the cache should use the stat() function
* instead of the lstat() function to test each path component.
*/
static int lstat_cache_matchlen(struct cache_def *cache,
const char *name, int len,
int *ret_flags, int track_flags,
int prefix_len_stat_func)
{
int match_len, last_slash, last_slash_dir, previous_slash;
int save_flags, max_len, ret;
struct stat st;
if (cache->track_flags != track_flags ||
cache->prefix_len_stat_func != prefix_len_stat_func) {
/*
* As a safeguard rule we clear the cache if the
* values of track_flags and/or prefix_len_stat_func
* does not match with the last supplied values.
*/
reset_lstat_cache(cache);
cache->track_flags = track_flags;
cache->prefix_len_stat_func = prefix_len_stat_func;
match_len = last_slash = 0;
} else {
/*
* Check to see if we have a match from the cache for
* the 2 "excluding" path types.
*/
match_len = last_slash =
longest_path_match(name, len, cache->path, cache->len,
&previous_slash);
*ret_flags = cache->flags & track_flags & (FL_NOENT|FL_SYMLINK);
if (!(track_flags & FL_FULLPATH) && match_len == len)
match_len = last_slash = previous_slash;
if (*ret_flags && match_len == cache->len)
return match_len;
/*
* If we now have match_len > 0, we would know that
* the matched part will always be a directory.
*
* Also, if we are tracking directories and 'name' is
* a substring of the cache on a path component basis,
* we can return immediately.
*/
*ret_flags = track_flags & FL_DIR;
if (*ret_flags && len == match_len)
return match_len;
}
/*
* Okay, no match from the cache so far, so now we have to
* check the rest of the path components.
*/
*ret_flags = FL_DIR;
last_slash_dir = last_slash;
max_len = len < PATH_MAX ? len : PATH_MAX;
while (match_len < max_len) {
do {
cache->path[match_len] = name[match_len];
match_len++;
} while (match_len < max_len && name[match_len] != '/');
if (match_len >= max_len && !(track_flags & FL_FULLPATH))
break;
last_slash = match_len;
cache->path[last_slash] = '\0';
if (last_slash <= prefix_len_stat_func)
ret = stat(cache->path, &st);
else
ret = lstat(cache->path, &st);
if (ret) {
*ret_flags = FL_LSTATERR;
if (errno == ENOENT)
*ret_flags |= FL_NOENT;
} else if (S_ISDIR(st.st_mode)) {
last_slash_dir = last_slash;
continue;
} else if (S_ISLNK(st.st_mode)) {
*ret_flags = FL_SYMLINK;
} else {
*ret_flags = FL_ERR;
}
break;
}
/*
* At the end update the cache. Note that max 3 different
* path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
* for the moment!
*/
save_flags = *ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
if (save_flags && last_slash > 0 && last_slash <= PATH_MAX) {
cache->path[last_slash] = '\0';
cache->len = last_slash;
cache->flags = save_flags;
} else if ((track_flags & FL_DIR) &&
last_slash_dir > 0 && last_slash_dir <= PATH_MAX) {
/*
* We have a separate test for the directory case,
* since it could be that we have found a symlink or a
* non-existing directory and the track_flags says
* that we cannot cache this fact, so the cache would
* then have been left empty in this case.
*
* But if we are allowed to track real directories, we
* can still cache the path components before the last
* one (the found symlink or non-existing component).
*/
cache->path[last_slash_dir] = '\0';
cache->len = last_slash_dir;
cache->flags = FL_DIR;
} else {
reset_lstat_cache(cache);
}
return match_len;
}
static int lstat_cache(struct cache_def *cache, const char *name, int len,
int track_flags, int prefix_len_stat_func)
{
int flags;
(void)lstat_cache_matchlen(cache, name, len, &flags, track_flags,
prefix_len_stat_func);
return flags;
}
#define USE_ONLY_LSTAT 0
/*
* Return non-zero if path 'name' has a leading symlink component
*/
int threaded_has_symlink_leading_path(struct cache_def *cache, const char *name, int len)
{
return lstat_cache(cache, name, len, FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) & FL_SYMLINK;
}
/*
* Return non-zero if path 'name' has a leading symlink component
*/
int has_symlink_leading_path(const char *name, int len)
{
return threaded_has_symlink_leading_path(&default_cache, name, len);
}
/*
* Return zero if path 'name' has a leading symlink component or
* if some leading path component does not exists.
*
* Return -1 if leading path exists and is a directory.
*
* Return path length if leading path exists and is neither a
* directory nor a symlink.
*/
int check_leading_path(const char *name, int len)
{
struct cache_def *cache = &default_cache; /* FIXME */
int flags;
int match_len = lstat_cache_matchlen(cache, name, len, &flags,
FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT);
if (flags & FL_NOENT)
return 0;
else if (flags & FL_DIR)
return -1;
else
return match_len;
}
/*
* Return non-zero if all path components of 'name' exists as a
* directory. If prefix_len > 0, we will test with the stat()
* function instead of the lstat() function for a prefix length of
* 'prefix_len', thus we then allow for symlinks in the prefix part as
* long as those points to real existing directories.
*/
int has_dirs_only_path(const char *name, int len, int prefix_len)
{
struct cache_def *cache = &default_cache; /* FIXME */
return lstat_cache(cache, name, len,
FL_DIR|FL_FULLPATH, prefix_len) &
FL_DIR;
}
static struct removal_def {
char path[PATH_MAX];
int len;
} removal;
static void do_remove_scheduled_dirs(int new_len)
{
while (removal.len > new_len) {
removal.path[removal.len] = '\0';
if (rmdir(removal.path))
break;
do {
removal.len--;
} while (removal.len > new_len &&
removal.path[removal.len] != '/');
}
removal.len = new_len;
}
void schedule_dir_for_removal(const char *name, int len)
{
int match_len, last_slash, i, previous_slash;
match_len = last_slash = i =
longest_path_match(name, len, removal.path, removal.len,
&previous_slash);
/* Find last slash inside 'name' */
while (i < len) {
if (name[i] == '/')
last_slash = i;
i++;
}
/*
* If we are about to go down the directory tree, we check if
* we must first go upwards the tree, such that we then can
* remove possible empty directories as we go upwards.
*/
if (match_len < last_slash && match_len < removal.len)
do_remove_scheduled_dirs(match_len);
/*
* If we go deeper down the directory tree, we only need to
* save the new path components as we go down.
*/
if (match_len < last_slash) {
memcpy(&removal.path[match_len], &name[match_len],
last_slash - match_len);
removal.len = last_slash;
}
}
void remove_scheduled_dirs(void)
{
do_remove_scheduled_dirs(0);
}