Merge branch 'tb/unexpected'

Code tightening against a "wrong" object appearing where an object
of a different type is expected, instead of blindly assuming that
the connection between objects are correctly made.

* tb/unexpected:
  rev-list: detect broken root trees
  rev-list: let traversal die when --missing is not in use
  get_commit_tree(): return NULL for broken tree
  list-objects.c: handle unexpected non-tree entries
  list-objects.c: handle unexpected non-blob entries
  t: introduce tests for unexpected object types
  t: move 'hex2oct' into test-lib-functions.sh

t/test-lib-functions.sh

@@ -1239,6 +1239,12 @@ depacketize () {
 	'
 }
 
+# Converts base-16 data into base-8. The output is given as a sequence of
+# escaped octals, suitable for consumption by 'printf'.
+hex2oct () {
+	perl -ne 'printf "\\%03o", hex for /../g'
+}
+
 # Set the hash algorithm in use to $1.  Only useful when testing the testsuite.
 test_set_hash () {
 	test_hash_algo="$1"