+On the other hand, when 'git gc' runs concurrently with another process,
+there is a risk of it deleting an object that the other process is using
+but hasn't created a reference to. This may just cause the other process
+to fail or may corrupt the repository if the other process later adds a
+reference to the deleted object. Git has two features that significantly
+mitigate this problem:
+
+. Any object with modification time newer than the `--prune` date is kept,
+ along with everything reachable from it.
+
+. Most operations that add an object to the database update the
+ modification time of the object if it is already present so that #1
+ applies.
+
+However, these features fall short of a complete solution, so users who
+run commands concurrently have to live with some risk of corruption (which
+seems to be low in practice) unless they turn off automatic garbage
+collection with 'git config gc.auto 0'.
+