`nullSha1`::
(WARN) Tree contains entries pointing to a null sha1.
-`symlinkPointsToGitDir`::
- (WARN) Symbolic link points inside a gitdir.
-
-`symlinkTargetBlob`::
- (ERROR) A non-blob found instead of a symbolic link's target.
-
-`symlinkTargetLength`::
- (WARN) Symbolic link target longer than maximum path length.
-
-`symlinkTargetMissing`::
- (ERROR) Unable to read symbolic link target's blob.
-
`treeNotSorted`::
(ERROR) A tree is not properly sorted.