Re: repository corruption when pushing commits to a repository running 'git gc --prune='

Matthieu Moy [off-list ref] writes:

I think this is the expected behavior. push will create new objects that
are not referenced until the ref is updated (at the very end). prune can
run concurrently since creating and deleting objects is done in a
lockless way (only the ref update needs a lock).

Still, this is not the *documented* behavior, and an easy way to corrupt
a repo should be very explicitly documented as very dangerous, and the
precautions to take when using it should be explained clearly.

Yeah, I think this paragraph in the user-manual is the only thing
that mentions it:

    Anyway, once you are sure that you're not interested in any dangling
    state, you can just prune all unreachable objects:

    ------------------------------------------------
    $ git prune
    ------------------------------------------------

    and they'll be gone. (You should only run `git prune` on a quiescent
    repository--it's kind of like doing a filesystem fsck recovery: you
    don't want to do that while the filesystem is mounted.

Something along this line, perhaps?

 Documentation/git-gc.txt | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Documentation/git-gc.txt b/Documentation/git-gc.txt
index 5223498..fa15104 100644
--- a/Documentation/git-gc.txt
+++ b/Documentation/git-gc.txt

@@ -63,8 +63,11 @@ automatic consolidation of packs.
 --prune=<date>::
 	Prune loose objects older than date (default is 2 weeks ago,
 	overridable by the config variable `gc.pruneExpire`).
-	--prune=all prunes loose objects regardless of their age.
-	--prune is on by default.
+	--prune=all prunes loose objects regardless of their age (do
+	not use --prune=all unless you know exactly what you are doing.
+	Unless the repository is quiescent, you will lose newly created
+	objects that haven't been anchored with the refs and end up
+	corrupting your repository).  --prune is on by default.
 
 --no-prune::
 	Do not prune any loose objects.