git-fetch --upload-pack: disambiguate.

diff --git a/read-cache.c b/read-cache.c
index 780601f071a0f5ae35b6d379abdd935d79ca92e2..c5474d49758b640f8942b1e3eb1a1c8f47c78ed8 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -87,7 +87,7 @@ static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
        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;
 
@@ -143,6 +143,13 @@ int ce_match_stat(struct cache_entry *ce, struct stat *st)
        if (ce->ce_size != htonl(st->st_size))
                changed |= DATA_CHANGED;
 
+       return changed;
+}
+
+int ce_match_stat(struct cache_entry *ce, struct stat *st)
+{
+       unsigned int changed = ce_match_stat_basic(ce, st);
+
        /*
         * Within 1 second of this sequence:
         *      echo xyzzy >file && git-update-index --add file
@@ -594,6 +601,50 @@ 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;
@@ -616,6 +667,9 @@ int write_cache(int newfd, struct cache_entry **cache, int entries)
                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;
        }