Make "update-cache --refresh" do what it really should do: just

refresh the "stat" information.

We need this after having done a "read-tree", for example, when the
stat information does not match the checked-out tree, and we want to
start getting efficient cache matching against the parts of the tree
that are already up-to-date.

diff --git a/update-cache.c b/update-cache.c
index 942e309..68a0ae0 100644 (file)
--- a/update-cache.c
+++ b/update-cache.c
@@ -57,6 +57,23 @@ static int index_fd(const char *path, int namelen, struct cache_entry *ce, int f
        return write_sha1_buffer(ce->sha1, out, stream.total_out);
 }
 
+/*
+ * This only updates the "non-critical" parts of the directory
+ * cache, ie the parts that aren't tracked by GIT, and only used
+ * to validate the cache.
+ */
+static void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
+{
+       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_uid = st->st_uid;
+       ce->st_gid = st->st_gid;
+}
+
 static int add_file_to_cache(char *path)
 {
        int size, namelen;
@@ -81,15 +98,8 @@ static int add_file_to_cache(char *path)
        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;
+       fill_stat_cache_info(ce, &st);
        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;
 
@@ -99,26 +109,96 @@ static int add_file_to_cache(char *path)
        return add_cache_entry(ce, allow_add);
 }
 
-static void refresh_entry(struct cache_entry *ce)
+static int match_data(int fd, void *buffer, unsigned long size)
+{
+       while (size) {
+               char compare[1024];
+               int ret = read(fd, compare, sizeof(compare));
+
+               if (ret <= 0 || ret > size || memcmp(buffer, compare, ret))
+                       return -1;
+               size -= ret;
+               buffer += ret;
+       }
+       return 0;
+}
+
+static int compare_data(struct cache_entry *ce)
+{
+       int match = -1;
+       int fd = open(ce->name, O_RDONLY);
+
+       if (fd >= 0) {
+               void *buffer;
+               unsigned long size;
+               char type[10];
+
+               buffer = read_sha1_file(ce->sha1, type, &size);
+               if (buffer) {
+                       if (size == ce->st_size && !strcmp(type, "blob"))
+                               match = match_data(fd, buffer, size);
+                       free(buffer);
+               }
+               close(fd);
+       }
+       return match;
+}
+
+/*
+ * "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 "read-tree",
+ * to link up the stat cache details with the proper files.
+ */
+static struct cache_entry *refresh_entry(struct cache_entry *ce)
 {
+       struct stat st;
+       struct cache_entry *updated;
+       int changed, size;
+
+       if (stat(ce->name, &st) < 0)
+               return NULL;
+
+       changed = cache_match_stat(ce, &st);
+       if (!changed)
+               return ce;
+
        /*
-        * This is really not the right way to do it, but
-        * add_file_to_cache() does do the right thing.
-        *
-        * We should really just update the cache
-        * entry in-place, I think. With this approach we
-        * end up allocating a new one, searching for where
-        * to insert it etc etc crud.
+        * If the length has changed, there's no point in trying
+        * to refresh the entry - it's not going to match
         */
-       add_file_to_cache(ce->name);
+       if (changed & (DATA_CHANGED | MODE_CHANGED))
+               return NULL;
+
+       if (compare_data(ce))
+               return NULL;
+
+       size = ce_size(ce);
+       updated = malloc(size);
+       memcpy(updated, ce, size);
+       fill_stat_cache_info(updated, &st);
+       return updated;
 }
 
 static void refresh_cache(void)
 {
        int i;
 
-       for (i = 0; i < active_nr; i++)
-               refresh_entry(active_cache[i]);
+       for (i = 0; i < active_nr; i++) {
+               struct cache_entry *ce = active_cache[i];
+               struct cache_entry *new = refresh_entry(ce);
+
+               if (!new) {
+                       printf("%s: needs update\n", ce->name);
+                       continue;
+               }
+               active_cache[i] = new;
+       }
 }
 
 /*