write_index: optionally allow broken null sha1s

diff --git a/read-cache.c b/read-cache.c
index d97e3bf7cdb025de06ecf339059c38976355d8a5..835070e24c45fd277ca75e2c4caeee84d71deb03 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -1800,8 +1800,17 @@ int write_index(struct index_state *istate, int newfd)
                        continue;
                if (!ce_uptodate(ce) && is_racy_timestamp(istate, ce))
                        ce_smudge_racily_clean_entry(ce);
-               if (is_null_sha1(ce->sha1))
-                       return error("cache entry has null sha1: %s", ce->name);
+               if (is_null_sha1(ce->sha1)) {
+                       static const char msg[] = "cache entry has null sha1: %s";
+                       static int allow = -1;
+
+                       if (allow < 0)
+                               allow = git_env_bool("GIT_ALLOW_NULL_SHA1", 0);
+                       if (allow)
+                               warning(msg, ce->name);
+                       else
+                               return error(msg, ce->name);
+               }
                if (ce_write_entry(&c, newfd, ce, previous_name) < 0)
                        return -1;
        }