Don't allow contrib/workdir/git-new-workdir to trash existing dirs

Recently I found that doing a sequence like the following:

  git-new-workdir a b
  ...
  git-new-workdir a b

by accident will cause a (and now also b) to have an infinite cycle
in its refs directory.  This is caused by git-new-workdir trying
to create the "refs" symlink over again, only during the second
time it is being created within a's refs directory and is now also
pointing back at a's refs.

This causes confusion in git as suddenly branches are named things
like "refs/refs/refs/refs/refs/refs/refs/heads/foo" instead of the
more commonly accepted "refs/heads/foo".  Plenty of commands start
to see ambiguous ref names and others just take ages to compute.

git-clone has the same safety check, so git-new-workdir should
behave just like it.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/contrib/workdir/git-new-workdir b/contrib/workdir/git-new-workdir
index c6e154a84fb5bdd4ed456ac3fdf94c54466fc5f0..2838546d16073f29b3a87ce9126d92b0f640be5e 100755 (executable)
--- a/contrib/workdir/git-new-workdir
+++ b/contrib/workdir/git-new-workdir
@@ -48,6 +48,12 @@ then
                "a complete repository."
 fi
 
+# don't recreate a workdir over an existing repository
+if test -e "$new_workdir"
+then
+       die "destination directory '$new_workdir' already exists."
+fi
+
 # make sure the the links use full paths
 git_dir=$(cd "$git_dir"; pwd)