hooks will not be invoked either. This can be useful to quickly
bail out if the update is not to be supported.
+See the notes on the quarantine environment below.
+
update Hook
-----------
Before each ref is updated, if $GIT_DIR/hooks/update file exists
exec git update-server-info
+Quarantine Environment
+----------------------
+
+When `receive-pack` takes in objects, they are placed into a temporary
+"quarantine" directory within the `$GIT_DIR/objects` directory and
+migrated into the main object store only after the `pre-receive` hook
+has completed. If the push fails before then, the temporary directory is
+removed entirely.
+
+This has a few user-visible effects and caveats:
+
+ 1. Pushes which fail due to problems with the incoming pack, missing
+ objects, or due to the `pre-receive` hook will not leave any
+ on-disk data. This is usually helpful to prevent repeated failed
+ pushes from filling up your disk, but can make debugging more
+ challenging.
+
+ 2. Any objects created by the `pre-receive` hook will be created in
+ the quarantine directory (and migrated only if it succeeds).
+
+ 3. The `pre-receive` hook MUST NOT update any refs to point to
+ quarantined objects. Other programs accessing the repository will
+ not be able to see the objects (and if the pre-receive hook fails,
+ those refs would become corrupted). For safety, any ref updates
+ from within `pre-receive` are automatically rejected.
+
+
SEE ALSO
--------
linkgit:git-send-pack[1], linkgit:gitnamespaces[7]