Merge branch 'jk/write-broken-index-with-nul-sha1'

Earlier we started rejecting an attempt to add 0{40} object name to
the index and to tree objects, but it sometimes is necessary to
allow so to be able to use tools like filter-branch to correct such
broken tree objects.

* jk/write-broken-index-with-nul-sha1:
  write_index: optionally allow broken null sha1s

1 files changed, 11 insertions, 2 deletions

diff --git a/read-cache.c b/read-cache.c
index 885943a6df..6bbe1b1fb3 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1818,8 +1818,17 @@ 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;
 	}