v5 for direct mode, with automatic upgrade

This includes storing the current state of the HEAD ref, which git annex
sync is going to need, but does not make sync use it.

3 files changed, 41 insertions, 4 deletions

diff --git a/doc/git-annex.mdwn b/doc/git-annex.mdwn
index d88957f9c..fd22fc672 100644
--- a/doc/git-annex.mdwn
+++ b/doc/git-annex.mdwn
@@ -698,12 +698,21 @@ subdirectories).
 
 * `pre-commit [path ...]`
 
+  This is meant to be called from git's pre-commit hook. `git annex init`
+  automatically creates a pre-commit hook using this.
+
   Fixes up symlinks that are staged as part of a commit, to ensure they
   point to annexed content. Also handles injecting changes to unlocked
   files into the annex.
 
-  This is meant to be called from git's pre-commit hook. `git annex init`
-  automatically creates a pre-commit hook using this.
+* `update-hook refname olvrev newrev`
+
+  This is meant to be called from git's update hook. `git annex init`
+  automatically creates an update hook using this.
+
+  This denies updates being pushed for the currently checked out branch.
+  While receive.denyCurrentBranch normally prevents that, it does
+  not for fake bare repositories, as used by direct mode.
 
 * `fromkey key file`
 
diff --git a/doc/todo/direct_mode_guard.mdwn b/doc/todo/direct_mode_guard.mdwn
index 6aab353fa..9fbb21cd3 100644
--- a/doc/todo/direct_mode_guard.mdwn
+++ b/doc/todo/direct_mode_guard.mdwn
@@ -77,6 +77,26 @@ This seems really promising. But of course, git-annex has its own set of
 behaviors in a bare repo, so will need to recognise that this repo is not
 really bare, and avoid them.
 
+> [[done]]!!  --[[Joey]]
+
 (Git may also have some bare repo behaviors that are unwanted. One example
 is that git allows pushes to the current branch in a bare repo, 
 even when `receive.denyCurrentBranch` is set.)
+
+> This is indeed a problem. Indeed, `git annex sync` successfully
+> pushes changes to the master branch of a fake bare direct mode repo.
+> 
+> And then, syncing in the repo that was pushed to causes the changes
+> that were pushed to the master branch to get reverted! This happens
+> because sync commits; commit sees that files are staged in index
+> differing from the (pushed) master, and commits the "changes"
+> which revert it.
+> 
+> Could fix this using an update hook, to reject the updated of the master
+> branch. However, won't work on crippled filesystems! (No +x bit)
+> 
+> Could make git annex sync detect this. It could reset the master
+> branch to the last one committed, before committing. Will work,
+> does have the minor oddity that eg `git log` will show commits
+> pushed to master before `git annex sync` has been run and so before
+> those commits are reflected in the tree.
diff --git a/doc/upgrades.mdwn b/doc/upgrades.mdwn
index 6cf54477c..5cf4093dc 100644
--- a/doc/upgrades.mdwn
+++ b/doc/upgrades.mdwn
@@ -18,10 +18,18 @@ conflicts first before upgrading git-annex.
 
 ## Upgrade events, so far
 
+### v4 -> v5 (git-annex version 5.x)
+
+v5 is only used for [[direct_mode]]. The upgrade from v4 to v5 is handled
+automatically.
+
+This upgrade involves changing direct mode repositories to operate with
+core.bare=true.
+
 ### v3 -> v4 (git-annex version 4.x)
 
-v4 is only used for [[direct_mode]], and no upgrade needs to be done from
-existing v3 repositories, they will continue to work.
+v4 was only used for [[direct_mode]], to ensure that a version of git-annex
+that understands direct mode was used with a direct mode repository. 
 
 ### v2 -> v3 (git-annex version 3.x)